diff --git a/qiskit_ibm_runtime/session.py b/qiskit_ibm_runtime/session.py
index 58b6eaa088..52c2f9a38c 100644
--- a/qiskit_ibm_runtime/session.py
+++ b/qiskit_ibm_runtime/session.py
@@ -253,6 +253,7 @@ def details(self) -> Optional[Dict[str, Any]]:
             last_job_completed: Timestamp of when the last job in the session completed.
             started_at: Timestamp of when the session was started.
             closed_at: Timestamp of when the session was closed.
+            activated_at: Timestamp of when the session state was changed to active.
         """
         if self._session_id:
             response = self._service._api_client.session_details(self._session_id)
@@ -269,6 +270,7 @@ def details(self) -> Optional[Dict[str, Any]]:
                     "last_job_completed": response.get("last_job_completed"),
                     "started_at": response.get("started_at"),
                     "closed_at": response.get("closed_at"),
+                    "activated_at": response.get("activated_at"),
                 }
         return None
 
diff --git a/releasenotes/notes/new-session-details-field-48311b4d3313ad94.yaml b/releasenotes/notes/new-session-details-field-48311b4d3313ad94.yaml
new file mode 100644
index 0000000000..ef6b210dc3
--- /dev/null
+++ b/releasenotes/notes/new-session-details-field-48311b4d3313ad94.yaml
@@ -0,0 +1,6 @@
+---
+features:
+  - |
+    :meth:`~qiskit_ibm_runtime.Session.details` has a new field, `activated_at`, which 
+    is the timestamp of when the session was changed to active.
+