diff --git a/gdc_ng_models/models/accessed.py b/gdc_ng_models/models/accessed.py
new file mode 100644
index 0000000..32db936
--- /dev/null
+++ b/gdc_ng_models/models/accessed.py
@@ -0,0 +1,23 @@
+"""Mixin for adding an accessed timestamp column to track the last time a record was accessed."""
+import datetime
+
+from sqlalchemy import schema, sql
+from sqlalchemy.sql import sqltypes
+
+
+class AccessedColumnMixin:
+    """A mixin to add accessed timestamp column to a data model.
+
+    Attributes:
+        accessed_datetime: Metadata describing when a row was last accessed.
+    """
+
+    def __init__(self):
+        pass
+
+    accessed_datetime = schema.Column(
+        sqltypes.DateTime(timezone=True),
+        nullable=False,
+        server_default=sql.text("now()"),
+        onupdate=datetime.datetime.utcnow,
+    )
diff --git a/gdc_ng_models/models/cohort.py b/gdc_ng_models/models/cohort.py
index 8fc7f56..ea33f6c 100644
--- a/gdc_ng_models/models/cohort.py
+++ b/gdc_ng_models/models/cohort.py
@@ -13,7 +13,7 @@
 import sqlalchemy
 from sqlalchemy.dialects import postgresql
 from sqlalchemy.ext import declarative
-from gdc_ng_models.models import audit
+from gdc_ng_models.models import accessed, audit
 
 Base = declarative.declarative_base()
 
@@ -73,7 +73,7 @@ def to_json(self):
         }
 
 
-class Cohort(Base, audit.AuditColumnsMixin):
+class Cohort(Base, audit.AuditColumnsMixin, accessed.AccessedColumnMixin):
     """A base definition for a cohort entity.
 
     Attributes:
@@ -81,7 +81,8 @@ class Cohort(Base, audit.AuditColumnsMixin):
         context_id: The ID of the associated context.
         name: A user defined name for the cohort.
         created_datetime: The date and time when the record is created.
-        updated_datetime: The date and time when the record is updated.
+        updated_datetime: The date and time when the record is last updated.
+        accessed_datetime: The date and time when the record is last accessed.
     """
 
     __tablename__ = "cohort"
@@ -121,7 +122,8 @@ def __repr__(self):
             "name='{name}', "
             "context_id={context_id}, "
             "created_datetime={created_datetime}, "
-            "updated_datetime={updated_datetime})>".format(
+            "updated_datetime={updated_datetime}), "
+            "accessed_datetime={accessed_datetime})>".format(
                 id=self.id,
                 name=self.name,
                 context_id=self.context_id,
@@ -131,6 +133,9 @@ def __repr__(self):
                 updated_datetime=self.updated_datetime.isoformat()
                 if self.updated_datetime
                 else None,
+                accessed_datetime=self.accessed_datetime.isoformat()
+                if self.accessed_datetime
+                else None,
             )
         )
 
@@ -145,6 +150,9 @@ def to_json(self):
             "updated_datetime": self.updated_datetime.isoformat()
             if self.updated_datetime
             else None,
+            "accessed_datetime": self.accessed_datetime.isoformat()
+            if self.accessed_datetime
+            else None,
         }
 
 
diff --git a/tests/integration/models/test_cohort.py b/tests/integration/models/test_cohort.py
index c0b666d..4d59d59 100644
--- a/tests/integration/models/test_cohort.py
+++ b/tests/integration/models/test_cohort.py
@@ -320,6 +320,7 @@ def test_cohort__to_json(create_cohort_db, db_session, fixture_context):
                 "context_id": str(test_cohort.context_id),
                 "created_datetime": test_cohort.created_datetime.isoformat(),
                 "updated_datetime": test_cohort.updated_datetime.isoformat(),
+                "accessed_datetime": test_cohort.accessed_datetime.isoformat(),
             }
         )
     )