diff --git a/sdk/core/azure-core/CHANGELOG.md b/sdk/core/azure-core/CHANGELOG.md
index 811230155bbb..97e8df98391e 100644
--- a/sdk/core/azure-core/CHANGELOG.md
+++ b/sdk/core/azure-core/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 ### Features Added
 
+- `azure.core.serialization.AzureJSONEncoder` (introduced in 1.17.0) serializes `datetime.datetime` objects in ISO 8601 format, conforming to RFC 3339's specification.    #20190
 - We now use `azure.core.serialization.AzureJSONEncoder` to serialize `json` input to `azure.core.rest.HttpRequest`.
 
 ### Breaking Changes in the Provisional `azure.core.rest` package
diff --git a/sdk/core/azure-core/azure/core/serialization.py b/sdk/core/azure-core/azure/core/serialization.py
index a7022aad131b..ef388f14cf26 100644
--- a/sdk/core/azure-core/azure/core/serialization.py
+++ b/sdk/core/azure-core/azure/core/serialization.py
@@ -105,8 +105,11 @@ def default(self, o):  # pylint: disable=too-many-return-statements
                 if hasattr(o, "year") and hasattr(o, "hour"):
                     # astimezone() fails for naive times in Python 2.7, so make make sure o is aware (tzinfo is set)
                     if not o.tzinfo:
-                        return o.replace(tzinfo=TZ_UTC).isoformat()
-                    return o.astimezone(TZ_UTC).isoformat()
+                        iso_formatted = o.replace(tzinfo=TZ_UTC).isoformat()
+                    else:
+                        iso_formatted = o.astimezone(TZ_UTC).isoformat()
+                    # Replace the trailing "+00:00" UTC offset with "Z" (RFC 3339: https://www.ietf.org/rfc/rfc3339.txt)
+                    return iso_formatted.replace("+00:00", "Z")
                 # Next try datetime.date or datetime.time
                 return o.isoformat()
             except AttributeError:
diff --git a/sdk/core/azure-core/tests/test_serialization.py b/sdk/core/azure-core/tests/test_serialization.py
index e7a4980cdc9f..41f2914cf343 100644
--- a/sdk/core/azure-core/tests/test_serialization.py
+++ b/sdk/core/azure-core/tests/test_serialization.py
@@ -150,7 +150,7 @@ def test_dictionary_datetime(json_dumps_with_encoder):
     expected = {
         "timedelta": "P1DT00H00M00S",
         "date": "2021-05-12",
-        "datetime": '2012-02-24T00:53:52.780000+00:00',
+        "datetime": '2012-02-24T00:53:52.780000Z',
         'time': '11:12:13',
     }
     assert json.loads(json_dumps_with_encoder(test_obj)) == expected
@@ -167,7 +167,7 @@ def __init__(self):
     expected_dict = {
         "timedelta": "P1DT00H00M00S",
         "date": "2021-05-12",
-        "datetime": '2012-02-24T00:53:52.780000+00:00',
+        "datetime": '2012-02-24T00:53:52.780000Z',
         'time': '11:12:13',
     }
     assert json.loads(json_dumps_with_encoder(expected.to_dict())) == expected_dict
@@ -205,10 +205,10 @@ def __init__(self):
     expected_dict = {
         "_attributes": {
             "enabled": True,
-            "not_before": "2012-02-24T00:53:52.780000+00:00",
-            "expires": "2032-02-24T00:53:52.780000+00:00",
-            "created": "2020-02-24T00:53:52.780000+00:00",
-            "updated": "2021-02-24T00:53:52.780000+00:00",
+            "not_before": "2012-02-24T00:53:52.780000Z",
+            "expires": "2032-02-24T00:53:52.780000Z",
+            "created": "2020-02-24T00:53:52.780000Z",
+            "updated": "2021-02-24T00:53:52.780000Z",
         },
         "_id": "id",
         "_vault_id": {
@@ -229,39 +229,39 @@ def test_serialize_datetime(json_dumps_with_encoder):
     date_obj = datetime.strptime('2015-01-01T00:00:00', "%Y-%m-%dT%H:%M:%S")
     date_str = json_dumps_with_encoder(date_obj)
 
-    assert date_str == '"2015-01-01T00:00:00+00:00"'
+    assert date_str == '"2015-01-01T00:00:00Z"'
 
     date_obj = datetime.strptime('1999-12-31T23:59:59', "%Y-%m-%dT%H:%M:%S").replace(tzinfo=NegativeUtcOffset())
     date_str = json_dumps_with_encoder(date_obj)
 
-    assert date_str == '"2000-01-01T11:59:59+00:00"'
+    assert date_str == '"2000-01-01T11:59:59Z"'
 
     date_obj = datetime.strptime("2015-06-01T16:10:08.0121", "%Y-%m-%dT%H:%M:%S.%f").replace(tzinfo=PositiveUtcOffset())
     date_str = json_dumps_with_encoder(date_obj)
 
-    assert date_str == '"2015-06-01T04:10:08.012100+00:00"'
+    assert date_str == '"2015-06-01T04:10:08.012100Z"'
 
     date_obj = datetime.min
     date_str = json_dumps_with_encoder(date_obj)
-    assert date_str == '"0001-01-01T00:00:00+00:00"'
+    assert date_str == '"0001-01-01T00:00:00Z"'
 
     date_obj = datetime.max
     date_str = json_dumps_with_encoder(date_obj)
-    assert date_str == '"9999-12-31T23:59:59.999999+00:00"'
+    assert date_str == '"9999-12-31T23:59:59.999999Z"'
 
     date_obj = datetime.strptime('2012-02-24T00:53:52.000001Z', "%Y-%m-%dT%H:%M:%S.%fZ")
     date_str = json_dumps_with_encoder(date_obj)
-    assert date_str == '"2012-02-24T00:53:52.000001+00:00"'
+    assert date_str == '"2012-02-24T00:53:52.000001Z"'
 
     date_obj = datetime.strptime('2012-02-24T00:53:52.780Z', "%Y-%m-%dT%H:%M:%S.%fZ")
     date_str = json_dumps_with_encoder(date_obj)
-    assert date_str == '"2012-02-24T00:53:52.780000+00:00"'
+    assert date_str == '"2012-02-24T00:53:52.780000Z"'
 
 def test_serialize_datetime_subclass(json_dumps_with_encoder):
 
     date_obj = DatetimeSubclass.strptime('2012-02-24T00:53:52.780Z', "%Y-%m-%dT%H:%M:%S.%fZ")
     date_str = json_dumps_with_encoder(date_obj)
-    assert date_str == '"2012-02-24T00:53:52.780000+00:00"'
+    assert date_str == '"2012-02-24T00:53:52.780000Z"'
 
 def test_serialize_time(json_dumps_with_encoder):