diff --git a/apps/api/src/app/groups/dto/create-union-group.dto.ts b/apps/api/src/app/groups/dto/create-union-group.dto.ts
new file mode 100644
index 00000000..2fcc2919
--- /dev/null
+++ b/apps/api/src/app/groups/dto/create-union-group.dto.ts
@@ -0,0 +1,40 @@
+import {
+    ArrayNotEmpty,
+    IsArray,
+    IsNumber,
+    IsString,
+    Length,
+    Max,
+    Min,
+    MinLength,
+    NotContains
+} from "class-validator"
+import { ApiProperty } from "@nestjs/swagger"
+
+export class CreateUnionGroupDto {
+    @IsString()
+    @Length(1, 50)
+    @NotContains("admin-groups")
+    @ApiProperty()
+    readonly name: string
+
+    @IsString()
+    @MinLength(10)
+    @ApiProperty()
+    readonly description: string
+
+    @IsNumber()
+    @Min(16, { message: "The tree depth must be between 16 and 32." })
+    @Max(32, { message: "The tree depth must be between 16 and 32." })
+    @ApiProperty()
+    readonly treeDepth: number
+
+    @IsNumber()
+    @Min(0)
+    @ApiProperty()
+    readonly fingerprintDuration: number
+    @IsArray()
+    @ArrayNotEmpty()
+    @ApiProperty()
+    readonly groupIds: string[]
+}
diff --git a/apps/api/src/app/groups/groups.controller.ts b/apps/api/src/app/groups/groups.controller.ts
index bf1bc24e..0343571c 100644
--- a/apps/api/src/app/groups/groups.controller.ts
+++ b/apps/api/src/app/groups/groups.controller.ts
@@ -31,6 +31,7 @@ import { UpdateGroupsDto } from "./dto/update-groups.dto"
 import { GroupsService } from "./groups.service"
 import { mapGroupToResponseDTO } from "./groups.utils"
 import { RemoveGroupsDto } from "./dto/remove-groups.dto"
+import { CreateUnionGroupDto } from "./dto/create-union-group.dto"
 
 @ApiTags("groups")
 @Controller("groups")
@@ -108,6 +109,40 @@ export class GroupsController {
         return groupsToResponseDTO
     }
 
+    @Post("union")
+    @ApiBody({ type: CreateUnionGroupDto })
+    @ApiHeader({ name: "x-api-key", required: true })
+    @ApiCreatedResponse({ type: Group })
+    @ApiOperation({
+        description: "Create a union group using an API Key or a valid session."
+    })
+    async createUnionGroup(
+        @Body() dto: CreateUnionGroupDto,
+        @Headers() headers: Headers,
+        @Req() req: Request
+    ) {
+        let group: any
+        const apiKey = headers["x-api-key"] as string
+
+        if (apiKey) {
+            group = await this.groupsService.createUnionGroupWithApiKey(
+                dto,
+                apiKey
+            )
+        } else if (req.session.adminId) {
+            group = await this.groupsService.createUnionGroupManually(
+                dto,
+                req.session.adminId
+            )
+        } else {
+            throw new NotImplementedException()
+        }
+
+        const fingerprint = await this.groupsService.getFingerprint(group.id)
+
+        return mapGroupToResponseDTO(group, fingerprint)
+    }
+
     @Delete()
     @ApiBody({ type: RemoveGroupsDto })
     @ApiHeader({ name: "x-api-key", required: true })
diff --git a/apps/api/src/app/groups/groups.service.test.ts b/apps/api/src/app/groups/groups.service.test.ts
index 95792863..3f037bfc 100644
--- a/apps/api/src/app/groups/groups.service.test.ts
+++ b/apps/api/src/app/groups/groups.service.test.ts
@@ -13,6 +13,7 @@ import { AdminsModule } from "../admins/admins.module"
 import { Admin } from "../admins/entities/admin.entity"
 import { CreateGroupDto } from "./dto/create-group.dto"
 import { UpdateGroupDto } from "./dto/update-group.dto"
+import { CreateUnionGroupDto } from "./dto/create-union-group.dto"
 
 jest.mock("@bandada/utils", () => {
     const originalModule = jest.requireActual("@bandada/utils")
@@ -796,6 +797,174 @@ describe("GroupsService", () => {
         })
     })
 
+    describe("# Create union group via API", () => {
+        const unionGroupDto: CreateUnionGroupDto = {
+            name: "Union Group API 1",
+            description: "This is a new union group",
+            treeDepth: 16,
+            fingerprintDuration: 3600,
+            groupIds: []
+        }
+        let admin: Admin
+        let apiKey: string
+
+        beforeAll(async () => {
+            admin = await adminsService.create({
+                id: "admin",
+                address: "0x"
+            })
+
+            apiKey = await adminsService.updateApiKey(
+                admin.id,
+                ApiKeyActions.Generate
+            )
+
+            admin = await adminsService.findOne({ id: admin.id })
+        })
+
+        it("Should create a union group via API", async () => {
+            const groupsDto: Array<CreateGroupDto> = [
+                {
+                    name: "Ref Group API 1",
+                    description: "This is a new group1",
+                    treeDepth: 16,
+                    fingerprintDuration: 3600
+                },
+                {
+                    name: "Ref Group API 2",
+                    description: "This is a new group2",
+                    treeDepth: 16,
+                    fingerprintDuration: 3600
+                }
+            ]
+
+            const groupIds = []
+
+            const groupDto: CreateUnionGroupDto = {
+                name: "Union Group API 1",
+                description: "This is a new group1",
+                treeDepth: 16,
+                fingerprintDuration: 3600,
+                groupIds
+            }
+
+            const groups = await groupsService.createGroupsWithAPIKey(
+                groupsDto,
+                apiKey
+            )
+
+            for await (const [i, group] of groups.entries()) {
+                await groupsService.addMemberManually(
+                    group.id,
+                    `${i}`,
+                    admin.id
+                )
+
+                groupIds.push(group.id)
+            }
+
+            const group = await groupsService.createUnionGroupWithApiKey(
+                groupDto,
+                apiKey
+            )
+
+            expect(group.adminId).toBe(admin.id)
+            expect(group.description).toBe(groupDto.description)
+            expect(group.name).toBe(groupDto.name)
+            expect(group.treeDepth).toBe(groupDto.treeDepth)
+            expect(group.fingerprintDuration).toBe(groupDto.fingerprintDuration)
+            expect(group.members).toHaveLength(2)
+            expect(group.credentials).toBeNull()
+        })
+
+        it("Should not add duplicate members to the union group", async () => {
+            const groupsDto: Array<CreateGroupDto> = [
+                {
+                    name: "Ref Group API 3",
+                    description: "This is a new group3",
+                    treeDepth: 16,
+                    fingerprintDuration: 3600
+                },
+                {
+                    name: "Ref Group API 4",
+                    description: "This is a new group4",
+                    treeDepth: 16,
+                    fingerprintDuration: 3600
+                }
+            ]
+
+            const groupIds = []
+
+            const groupDto: CreateUnionGroupDto = {
+                name: "Union Group API 2",
+                description: "This is a new group2",
+                treeDepth: 16,
+                fingerprintDuration: 3600,
+                groupIds
+            }
+
+            const groups = await groupsService.createGroupsWithAPIKey(
+                groupsDto,
+                apiKey
+            )
+
+            for await (const group of groups) {
+                await groupsService.addMemberManually(group.id, "1", admin.id)
+
+                groupIds.push(group.id)
+            }
+
+            await groupsService.createUnionGroupWithApiKey(groupDto, apiKey)
+
+            const group = await groupsService.createUnionGroupWithApiKey(
+                groupDto,
+                apiKey
+            )
+
+            expect(group.adminId).toBe(admin.id)
+            expect(group.description).toBe(groupDto.description)
+            expect(group.name).toBe(groupDto.name)
+            expect(group.treeDepth).toBe(groupDto.treeDepth)
+            expect(group.fingerprintDuration).toBe(groupDto.fingerprintDuration)
+            expect(group.members).toHaveLength(1)
+        })
+
+        it("Should not create a union group if the admin does not exist", async () => {
+            const fun = groupsService.createUnionGroupWithApiKey(
+                unionGroupDto,
+                "wrong"
+            )
+
+            await expect(fun).rejects.toThrow(
+                `Invalid API key or invalid admin for the groups`
+            )
+        })
+
+        it("Should not create a union group if the API key is invalid", async () => {
+            const fun = groupsService.createUnionGroupWithApiKey(
+                unionGroupDto,
+                "apiKey"
+            )
+
+            await expect(fun).rejects.toThrow(
+                `Invalid API key or invalid admin for the groups`
+            )
+        })
+
+        it("Should not create a union group if the API key is disabled for the admin", async () => {
+            await adminsService.updateApiKey(admin.id, ApiKeyActions.Disable)
+
+            const fun = groupsService.createUnionGroupWithApiKey(
+                unionGroupDto,
+                apiKey
+            )
+
+            await expect(fun).rejects.toThrow(
+                `Invalid API key or API access not enabled for admin '${admin.id}'`
+            )
+        })
+    })
+
     describe("# Update group via API", () => {
         const groupDto: CreateGroupDto = {
             id: "1",
@@ -1582,6 +1751,140 @@ describe("GroupsService", () => {
         })
     })
 
+    describe("# createUnionGroupManually", () => {
+        let admin: Admin
+
+        beforeAll(async () => {
+            admin = await adminsService.create({
+                id: "admin",
+                address: "0x"
+            })
+        })
+
+        it("Should create a union group manually", async () => {
+            const groupsDto: Array<CreateGroupDto> = [
+                {
+                    name: "Ref Group 1",
+                    description: "This is a new group1",
+                    treeDepth: 16,
+                    fingerprintDuration: 3600
+                },
+                {
+                    name: "Ref Group 2",
+                    description: "This is a new group2",
+                    treeDepth: 16,
+                    fingerprintDuration: 7200
+                }
+            ]
+
+            const groupIds = []
+
+            const groupDto: CreateUnionGroupDto = {
+                name: "Union Group 1",
+                description: "This is a new group1",
+                treeDepth: 16,
+                fingerprintDuration: 3600,
+                groupIds
+            }
+
+            const groups = await groupsService.createGroupsManually(
+                groupsDto,
+                admin.id
+            )
+
+            for await (const [i, group] of groups.entries()) {
+                await groupsService.addMemberManually(
+                    group.id,
+                    `${i}`,
+                    admin.id
+                )
+
+                groupIds.push(group.id)
+            }
+
+            const group = await groupsService.createUnionGroupManually(
+                groupDto,
+                admin.id
+            )
+
+            expect(group.adminId).toBe(admin.id)
+            expect(group.description).toBe(groupDto.description)
+            expect(group.name).toBe(groupDto.name)
+            expect(group.treeDepth).toBe(groupDto.treeDepth)
+            expect(group.fingerprintDuration).toBe(groupDto.fingerprintDuration)
+            expect(group.members).toHaveLength(2)
+        })
+
+        it("Should not create a union group manually if the admin doesn't exist", async () => {
+            const groupIds = []
+
+            const groupDto: CreateUnionGroupDto = {
+                name: "Union Group 1",
+                description: "This is a new group1",
+                treeDepth: 16,
+                fingerprintDuration: 3600,
+                groupIds
+            }
+
+            const fun = groupsService.createUnionGroupManually(
+                groupDto,
+                "wrong"
+            )
+
+            await expect(fun).rejects.toThrow(`You are not an admin`)
+        })
+
+        it("Should not add duplicate members to the union group", async () => {
+            const groupsDto: Array<CreateGroupDto> = [
+                {
+                    name: "Ref Group 3",
+                    description: "This is a new group3",
+                    treeDepth: 16,
+                    fingerprintDuration: 3600
+                },
+                {
+                    name: "Ref Group 4",
+                    description: "This is a new group4",
+                    treeDepth: 16,
+                    fingerprintDuration: 3600
+                }
+            ]
+
+            const groupIds = []
+
+            const groupDto: CreateUnionGroupDto = {
+                name: "Union Group 2",
+                description: "This is a new group 2",
+                treeDepth: 16,
+                fingerprintDuration: 3600,
+                groupIds
+            }
+
+            const groups = await groupsService.createGroupsManually(
+                groupsDto,
+                admin.id
+            )
+
+            for await (const group of groups) {
+                await groupsService.addMemberManually(group.id, "1", admin.id)
+
+                groupIds.push(group.id)
+            }
+
+            const group = await groupsService.createUnionGroupManually(
+                groupDto,
+                admin.id
+            )
+
+            expect(group.adminId).toBe(admin.id)
+            expect(group.description).toBe(groupDto.description)
+            expect(group.name).toBe(groupDto.name)
+            expect(group.treeDepth).toBe(groupDto.treeDepth)
+            expect(group.fingerprintDuration).toBe(groupDto.fingerprintDuration)
+            expect(group.members).toHaveLength(1)
+        })
+    })
+
     describe("# removeGroupManually", () => {
         const groupDto: CreateGroupDto = {
             id: "1",
diff --git a/apps/api/src/app/groups/groups.service.ts b/apps/api/src/app/groups/groups.service.ts
index c0c7eae2..518094db 100644
--- a/apps/api/src/app/groups/groups.service.ts
+++ b/apps/api/src/app/groups/groups.service.ts
@@ -20,6 +20,7 @@ import { Group } from "./entities/group.entity"
 import { Member } from "./entities/member.entity"
 import { MerkleProof } from "./types"
 import { getAndCheckAdmin } from "../utils"
+import { CreateUnionGroupDto } from "./dto/create-union-group.dto"
 
 @Injectable()
 export class GroupsService {
@@ -138,6 +139,68 @@ export class GroupsService {
         return newGroups
     }
 
+    /**
+     * Creates a group that are union of existing groups using API Key.
+     * @param dto External parameters used to create a new group.
+     * @param groupIds Existing group ids.
+     * @param apiKey The API Key.
+     * @returns Created group.
+     */
+    async createUnionGroupWithApiKey(
+        dto: CreateUnionGroupDto,
+        apiKey: string
+    ): Promise<Group> {
+        let group = await this.createGroupWithAPIKey(dto, apiKey)
+
+        const members = []
+
+        for await (const groupId of dto.groupIds) {
+            const refGroup = await this.getGroup(groupId)
+
+            if (refGroup) {
+                for (const member of refGroup.members) {
+                    if (!members.includes(member.id)) {
+                        members.push(member.id)
+                    }
+                }
+            }
+        }
+
+        group = await this.addMembers(group.id, members)
+
+        return group
+    }
+
+    /**
+     * Creates a group that are union of existing groups manually without using API Key.
+     * @param dto External parameters used to create a new group.
+     * @param groupIds Existing group ids.
+     * @param adminId Admin id.
+     * @returns Created group.
+     */
+    async createUnionGroupManually(
+        dto: CreateUnionGroupDto,
+        adminId: string
+    ): Promise<Group> {
+        let group = await this.createGroupManually(dto, adminId)
+
+        const members = []
+
+        for await (const groupId of dto.groupIds) {
+            const refGroup = await this.getGroup(groupId)
+
+            if (refGroup) {
+                for (const member of refGroup.members) {
+                    members.push(member.id)
+                }
+            }
+        }
+
+        group = await this.addMembers(group.id, members)
+
+        return group
+    }
+
     /**
      * Creates a new group.
      * @param dto External parameters used to create a new group.
diff --git a/apps/docs/docs/api-sdk.md b/apps/docs/docs/api-sdk.md
index 9bd13bdf..accaa29c 100644
--- a/apps/docs/docs/api-sdk.md
+++ b/apps/docs/docs/api-sdk.md
@@ -202,6 +202,31 @@ const apiKey = "70f07d0d-6aa2-4fe1-b4b9-06c271a641dc"
 const groups = await apiSdk.createGroups(groupsCreateDetails, apiKey)
 ```
 
+## Create union group
+
+\# **createUnionGroup**(): _Promise\<Group>_
+
+Create a union group from multiple groups.
+
+```ts
+const unionGroupCreationDetails = {
+    name: "Group 1",
+    description: "This is Group 1",
+    treeDepth: 16,
+    fingerprintDuration: 3600,
+    groupIds: [
+        "10402173435763029700781503965100",
+        "20402173435763029700781503965200"
+    ]
+}
+const apiKey = "70f07d0d-6aa2-4fe1-b4b9-06c271a641dc"
+
+const unionGroup = await apiSdk.createUnionGroup(
+    unionGroupCreationDetails,
+    apiKey
+)
+```
+
 ## Remove group
 
 \# **removeGroup**(): _Promise\<void>_
diff --git a/libs/api-sdk/README.md b/libs/api-sdk/README.md
index 21e01288..8eb8d5ca 100644
--- a/libs/api-sdk/README.md
+++ b/libs/api-sdk/README.md
@@ -225,6 +225,31 @@ const apiKey = "70f07d0d-6aa2-4fe1-b4b9-06c271a641dc"
 const groups = await apiSdk.createGroups(groupsCreateDetails, apiKey)
 ```
 
+## Create union group
+
+\# **createUnionGroup**(): _Promise\<Group>_
+
+Create a union group from multiple groups.
+
+```ts
+const unionGroupCreationDetails = {
+    name: "Group 1",
+    description: "This is Group 1",
+    treeDepth: 16,
+    fingerprintDuration: 3600,
+    groupIds: [
+        "10402173435763029700781503965100",
+        "20402173435763029700781503965200"
+    ]
+}
+const apiKey = "70f07d0d-6aa2-4fe1-b4b9-06c271a641dc"
+
+const unionGroup = await apiSdk.createUnionGroup(
+    unionGroupCreationDetails,
+    apiKey
+)
+```
+
 ## Remove group
 
 \# **removeGroup**(): _Promise\<void>_
diff --git a/libs/api-sdk/src/apiSdk.ts b/libs/api-sdk/src/apiSdk.ts
index 822564dc..e5d62ede 100644
--- a/libs/api-sdk/src/apiSdk.ts
+++ b/libs/api-sdk/src/apiSdk.ts
@@ -4,7 +4,8 @@ import {
     Invite,
     GroupCreationDetails,
     GroupUpdateDetails,
-    DashboardUrl
+    DashboardUrl,
+    UnionGroupCreationDetails
 } from "./types"
 import checkParameter from "./checkParameter"
 import {
@@ -25,7 +26,8 @@ import {
     getGroupsByAdminId,
     getGroupsByMemberId,
     getCredentialGroupJoinUrl,
-    getMultipleCredentialsGroupJoinUrl
+    getMultipleCredentialsGroupJoinUrl,
+    createUnionGroup
 } from "./groups"
 import { createInvite, getInvite, redeemInvite } from "./invites"
 
@@ -138,6 +140,32 @@ export default class ApiSdk {
         return groups[0]
     }
 
+    /**
+     * Creates a union group using the API key.
+     * @param unionGroupCreationDetails Union group creation details.
+     * @param apiKey The API key of the admin of the group.
+     * @returns The created union group.
+     */
+    async createUnionGroup(
+        unionGroupCreationDetails: UnionGroupCreationDetails,
+        apiKey: string
+    ): Promise<Group> {
+        if (
+            unionGroupCreationDetails.treeDepth < 16 ||
+            unionGroupCreationDetails.treeDepth > 32
+        ) {
+            throw new Error("The tree depth must be between 16 and 32")
+        }
+
+        const group = await createUnionGroup(
+            this._config,
+            unionGroupCreationDetails,
+            apiKey
+        )
+
+        return group
+    }
+
     /**
      * Creates one or more groups using the API key.
      * @param groupsCreationDetails Data to create the groups.
diff --git a/libs/api-sdk/src/groups.ts b/libs/api-sdk/src/groups.ts
index 4cc9481f..073ec27a 100644
--- a/libs/api-sdk/src/groups.ts
+++ b/libs/api-sdk/src/groups.ts
@@ -3,7 +3,8 @@ import type {
     GroupCreationDetails,
     Group,
     GroupUpdateDetails,
-    DashboardUrl
+    DashboardUrl,
+    UnionGroupCreationDetails
 } from "./types"
 
 const url = "/groups"
@@ -132,6 +133,32 @@ export async function createGroups(
     return req
 }
 
+/**
+ * Creates a union group with the provided details.
+ * @param unionGroupCreationDetails Data to create the union group.
+ * @param apiKey API Key of the admin.
+ * @returns Created union group.
+ */
+export async function createUnionGroup(
+    config: object,
+    unionGroupCreationDetails: UnionGroupCreationDetails,
+    apiKey: string
+): Promise<Group> {
+    const requestUrl = `${url}/union`
+
+    const newConfig: any = {
+        method: "post",
+        data: unionGroupCreationDetails,
+        ...config
+    }
+
+    newConfig.headers["x-api-key"] = apiKey
+
+    const req = await request(requestUrl, newConfig)
+
+    return req
+}
+
 /**
  * Removes the group.
  * @param groupId The group id.
diff --git a/libs/api-sdk/src/index.test.ts b/libs/api-sdk/src/index.test.ts
index 6d3203d8..0628bc75 100644
--- a/libs/api-sdk/src/index.test.ts
+++ b/libs/api-sdk/src/index.test.ts
@@ -6,7 +6,8 @@ import {
     GroupUpdateDetails,
     Invite,
     SupportedUrl,
-    DashboardUrl
+    DashboardUrl,
+    UnionGroupCreationDetails
 } from "./types"
 import checkParameter from "./checkParameter"
 
@@ -323,6 +324,69 @@ describe("Bandada API SDK", () => {
                 )
             })
         })
+        describe("#createUnionGroup", () => {
+            it("Should create a union group", async () => {
+                const groups = [
+                    {
+                        id: "10402173435763029700781503965100",
+                        name: "Union Group 1",
+                        description: "This is a new group",
+                        admin: "0xdf558148e66850ac48dbe2c8119b0eefa7d08bfd19c997c90a142eb97916b847",
+                        treeDepth: 16,
+                        fingerprintDuration: 3600,
+                        members: ["1"]
+                    },
+                    {
+                        id: "20402173435763029700781503965200",
+                        name: "Union Group 2",
+                        description: "This is a new group",
+                        admin: "0xdf558148e66850ac48dbe2c8119b0eefa7d08bfd19c997c90a142eb97916b847",
+                        treeDepth: 32,
+                        fingerprintDuration: 7200,
+                        members: ["2"]
+                    }
+                ]
+
+                const expectedGroup: UnionGroupCreationDetails = {
+                    name: "Union Group 3",
+                    description: "This is a new group",
+                    treeDepth: 16,
+                    fingerprintDuration: 3600,
+                    groupIds: groups.map((group) => group.id)
+                }
+
+                const apiKey = "70f07d0d-6aa2-4fe1-b4b9-06c271a641dc"
+
+                requestMocked.mockImplementationOnce(() =>
+                    Promise.resolve({
+                        id: "30402173435763029700781503965300",
+                        name: "Union Group 3",
+                        description: "This is a new group",
+                        admin: "0xdf558148e66850ac48dbe2c8119b0eefa7d08bfd19c997c90a142eb97916b847",
+                        treeDepth: 16,
+                        fingerprintDuration: 3600,
+                        createdAt: "2023-07-15T08:21:05.000Z",
+                        members: ["1", "2"],
+                        credentials: null
+                    })
+                )
+
+                const apiSdk: ApiSdk = new ApiSdk(SupportedUrl.DEV)
+                const group: Group = await apiSdk.createUnionGroup(
+                    expectedGroup,
+                    apiKey
+                )
+
+                expect(group.description).toBe(expectedGroup.description)
+                expect(group.name).toBe(expectedGroup.name)
+                expect(group.treeDepth).toBe(expectedGroup.treeDepth)
+                expect(group.fingerprintDuration).toBe(
+                    expectedGroup.fingerprintDuration
+                )
+                expect(group.members).toHaveLength(2)
+            })
+        })
+
         describe("#removeGroup", () => {
             it("Should create a group", async () => {
                 const groupId = "10402173435763029700781503965100"
diff --git a/libs/api-sdk/src/types/index.ts b/libs/api-sdk/src/types/index.ts
index b78166c8..951b9bf2 100644
--- a/libs/api-sdk/src/types/index.ts
+++ b/libs/api-sdk/src/types/index.ts
@@ -21,6 +21,14 @@ export type GroupCreationDetails = {
     credentials?: Credential
 }
 
+export type UnionGroupCreationDetails = {
+    name: string
+    description: string
+    treeDepth: number
+    fingerprintDuration: number
+    groupIds: string[]
+}
+
 export type GroupUpdateDetails = {
     description?: string
     treeDepth?: number