diff --git a/inbox/api/kellogs.py b/inbox/api/kellogs.py
index f3acd3965..8716e5452 100644
--- a/inbox/api/kellogs.py
+++ b/inbox/api/kellogs.py
@@ -1,6 +1,6 @@
 import calendar
 import datetime
-from json import JSONEncoder, dumps
+from json import JSONEncoder, dumps, loads
 
 import arrow  # type: ignore[import-untyped]
 from flask import Response
@@ -76,6 +76,24 @@ def format_phone_numbers(phone_numbers):  # type: ignore[no-untyped-def]  # noqa
     return formatted_phone_numbers
 
 
+def _extract_extended_properties(
+    raw_data: str | None,
+) -> dict[str, dict[str, str]] | None:
+    """
+    Extract extendedProperties from an event's raw_data JSON.
+
+    Returns the extendedProperties dict if present, otherwise None.
+    This is Google Calendar specific data.
+    """
+    if not raw_data:
+        return None
+    try:
+        data = loads(raw_data)
+        return data.get("extendedProperties")
+    except (ValueError, TypeError):
+        return None
+
+
 def encode(  # type: ignore[no-untyped-def]  # noqa: ANN201
     obj, namespace_public_id=None, expand: bool = False, is_n1: bool = False
 ):
@@ -357,6 +375,7 @@ def _get_lowercase_class_name(obj):  # type: ignore[no-untyped-def]
             "uid": obj.uid,
             "calendar_event_link": obj.calendar_event_link,
             "conference_data": obj.conference_data,
+            "extended_properties": _extract_extended_properties(obj.raw_data),
         }
         if isinstance(obj, RecurringEvent):
             resp["recurrence"] = {
diff --git a/tests/events/test_google_events.py b/tests/events/test_google_events.py
index 66405be33..5236f3214 100644
--- a/tests/events/test_google_events.py
+++ b/tests/events/test_google_events.py
@@ -7,7 +7,7 @@
 import pytest
 import requests
 
-from inbox.api.kellogs import _encode
+from inbox.api.kellogs import _encode, _extract_extended_properties
 from inbox.events.google import GoogleEventsProvider, parse_event_response
 from inbox.exceptions import AccessNotEnabledError
 from inbox.models import Calendar, Event
@@ -859,3 +859,76 @@ def test_cancelled_override_creation() -> None:
     provider._get_raw_events = mock.MagicMock(return_value=raw_response)
     updates = provider.sync_events("uid", 1)
     assert updates[0].cancelled is True
+
+
+class TestExtractExtendedProperties:
+    """Tests for the _extract_extended_properties helper function."""
+
+    def test_returns_none_for_none_raw_data(self) -> None:
+        assert _extract_extended_properties(None) is None
+
+    def test_returns_none_for_empty_raw_data(self) -> None:
+        assert _extract_extended_properties("") is None
+
+    def test_returns_none_for_invalid_json(self) -> None:
+        assert _extract_extended_properties("not valid json") is None
+
+    def test_returns_none_when_extended_properties_not_present(self) -> None:
+        raw_data = json.dumps({"id": "test", "summary": "Test Event"})
+        assert _extract_extended_properties(raw_data) is None
+
+    def test_returns_extended_properties(self) -> None:
+        raw_data = json.dumps(
+            {
+                "id": "test",
+                "extendedProperties": {"private": {"key1": "value1"}},
+            }
+        )
+        result = _extract_extended_properties(raw_data)
+        assert result == {"private": {"key1": "value1"}}
+
+
+@pytest.mark.parametrize(
+    ("raw_extended_properties", "expected_extended_properties"),
+    [
+        ({}, None),
+        (
+            {"extendedProperties": {"private": {"closeTaskId": "task_123"}}},
+            {"private": {"closeTaskId": "task_123"}},
+        ),
+    ],
+)
+def test_event_with_extended_properties(
+    raw_extended_properties, expected_extended_properties
+) -> None:
+    raw_event = {
+        "created": "2014-01-09T03:33:02.000Z",
+        "creator": {
+            "displayName": "Ben Bitdiddle",
+            "email": "ben.bitdiddle2222@gmail.com",
+            "self": True,
+        },
+        "etag": '"2778476764000000"',
+        "htmlLink": "https://www.google.com/calendar/event?eid=BAR",
+        "iCalUID": "20140615_60o30dr564o30c1g60o30dr4ck@google.com",
+        "id": "20140615_60o30dr564o30c1g60o30dr4ck",
+        "kind": "calendar#event",
+        "organizer": {
+            "displayName": "Ben Bitdiddle",
+            "email": "ben.bitdiddle2222@gmail.com",
+            "self": True,
+        },
+        "sequence": 0,
+        "start": {"date": "2014-03-15"},
+        "end": {"date": "2014-03-15"},
+        "status": "confirmed",
+        "summary": "Event with Extended Properties",
+        "transparency": "transparent",
+        "updated": "2014-01-09T03:33:02.000Z",
+        "visibility": "public",
+        **raw_extended_properties,
+    }
+
+    event = parse_event_response(raw_event, True)
+    encoded = _encode(event, "999999")
+    assert encoded["extended_properties"] == expected_extended_properties