diff --git a/bundles/org.openhab.ui/web/src/components/thing/thing-general-settings.vue b/bundles/org.openhab.ui/web/src/components/thing/thing-general-settings.vue
index 0db5577a8b..729da814ee 100644
--- a/bundles/org.openhab.ui/web/src/components/thing/thing-general-settings.vue
+++ b/bundles/org.openhab.ui/web/src/components/thing/thing-general-settings.vue
@@ -7,7 +7,7 @@
             <f7-list inline-labels no-hairlines-md class="no-margin">
               <f7-list-input v-if="createMode" label="Thing ID" type="text" placeholder="Required" :value="thing.ID"
                              @input="changeUID" info="Note: cannot be changed after the creation"
-                             required validate pattern="[A-Za-z0-9_\-]+" error-message="Required. A-Z,a-z,0-9,_,- only" />
+                             required :error-message="idErrorMessage" :error-message-force="!!idErrorMessage" />
               <f7-list-input label="Thing UID" type="text" :input="false" disabled>
                 <span slot="input">
                   {{ thing.UID }}
@@ -43,9 +43,11 @@
 <script>
 import ThingPicker from '@/components/config/controls/thing-picker.vue'
 import ClipboardIcon from '@/components/util/clipboard-icon.vue'
+import ThingMixin from '@/components/thing/thing-mixin'
 
 export default {
-  props: ['thing', 'thingType', 'createMode', 'ready', 'readOnly'],
+  mixins: [ThingMixin],
+  props: ['thing', 'thingType', 'createMode', 'ready', 'readOnly', 'things'],
   components: {
     ThingPicker,
     ClipboardIcon
@@ -53,6 +55,9 @@ export default {
   computed: {
     editable () {
       return this.createMode || (this.thing && this.thing.editable)
+    },
+    idErrorMessage () {
+      return this.validateThingUID(this.thing.UID, this.thing.ID)
     }
   },
   methods: {
@@ -63,11 +68,11 @@ export default {
     },
     changeUID (event) {
       this.$set(this.thing, 'ID', event.target.value)
-      if (this.createMode) this.thing.UID = this.computedThingUid()
+      this.thing.UID = this.computedThingUid()
     },
     updateBridge (value) {
       this.thing.bridgeUID = value
-      if (this.createMode) this.thing.UID = this.computedThingUid()
+      this.thing.UID = this.computedThingUid()
     }
   }
 }
diff --git a/bundles/org.openhab.ui/web/src/components/thing/thing-mixin.js b/bundles/org.openhab.ui/web/src/components/thing/thing-mixin.js
new file mode 100644
index 0000000000..1a3b062e98
--- /dev/null
+++ b/bundles/org.openhab.ui/web/src/components/thing/thing-mixin.js
@@ -0,0 +1,21 @@
+export default {
+  methods: {
+    /**
+     * Validate the Thing ID against valid characters and
+     * if existing Things are available on `this.things`,
+     * ensures that the Thing UID doesn't match an existing UID.
+     *
+     * @param {string} uid The Thing UID to validate
+     * @param {string} id The Thing ID to validate
+     * @returns {string} The error message if either the ID or the UID are invalid, or an empty string if they are valid.
+     */
+    validateThingUID (uid, id) {
+      if (!/^[A-Za-z0-9_-]+$/.test(id)) {
+        return 'Required. Must not start with a number. A-Z,a-z,0-9,_ only'
+      } else if (this.things && this.things.some(thing => thing.UID === uid)) {
+        return `A Thing with '${uid}' UID already exists`
+      }
+      return ''
+    }
+  }
+}
diff --git a/bundles/org.openhab.ui/web/src/pages/settings/things/add/thing-add.vue b/bundles/org.openhab.ui/web/src/pages/settings/things/add/thing-add.vue
index 78b2053d71..ac67bbef9e 100644
--- a/bundles/org.openhab.ui/web/src/pages/settings/things/add/thing-add.vue
+++ b/bundles/org.openhab.ui/web/src/pages/settings/things/add/thing-add.vue
@@ -11,7 +11,7 @@
 
     <f7-block v-if="ready" class="block-narrow">
       <f7-col>
-        <thing-general-settings :thing="thing" :thing-type="thingType" :createMode="true" :ready="true" />
+        <thing-general-settings :thing="thing" :thing-type="thingType" :createMode="true" :things="things" :ready="true" />
         <f7-block-title medium>
           {{ thingType.label }}
         </f7-block-title>
@@ -61,13 +61,15 @@
 import ConfigSheet from '@/components/config/config-sheet.vue'
 
 import ThingGeneralSettings from '@/components/thing/thing-general-settings.vue'
+import ThingMixin from '@/components/thing/thing-mixin'
 
 export default {
+  mixins: [ThingMixin],
+  props: ['thingTypeId', 'thingCopy'],
   components: {
     ConfigSheet,
     ThingGeneralSettings
   },
-  props: ['thingTypeId', 'thingCopy'],
   data () {
     if (this.thingCopy) {
       delete this.thingCopy.editable
@@ -77,6 +79,7 @@ export default {
     return {
       ready: false,
       currentTab: 'info',
+      things: [],
       thing: this.thingCopy || {
         UID: '',
         label: '',
@@ -118,7 +121,10 @@ export default {
           }
         }
 
-        this.ready = true
+        this.$oh.api.get('/rest/things?summary=true&staticDataOnly=true').then((things) => {
+          this.things = things
+          this.ready = true
+        })
       })
     },
     save () {
@@ -126,6 +132,11 @@ export default {
         this.$f7.dialog.alert('Please give a unique identifier')
         return
       }
+      const uidValidationError = this.validateThingUID(this.thing.UID, this.thing.ID)
+      if (uidValidationError !== '') {
+        this.$f7.dialog.alert('Invalid Thing ID: ' + uidValidationError)
+        return
+      }
       if (!this.thing.label) {
         this.$f7.dialog.alert('Please give a name')
         return
@@ -140,14 +151,18 @@ export default {
         })
       }
 
-      this.$oh.api.post('/rest/things', this.thing).then(() => {
-        this.$f7.toast.create({
-          text: 'Thing created',
-          destroyOnClose: true,
-          closeTimeout: 2000
-        }).open()
-      })
-      setTimeout(() => { this.$f7router.navigate('/settings/things/', { reloadCurrent: true }) }, 300)
+      this.$oh.api.post('/rest/things', this.thing)
+        .then(() => {
+          this.$f7.toast.create({
+            text: 'Thing created',
+            destroyOnClose: true,
+            closeTimeout: 2000
+          }).open()
+          setTimeout(() => { this.$f7router.navigate('/settings/things/', { reloadCurrent: true }) }, 300)
+        })
+        .catch((error) => {
+          this.$f7.dialog.alert('Error creating Thing: ' + error)
+        })
     }
   }
 }