diff --git a/app/connectors_service/connectors/sources/mongo/datasource.py b/app/connectors_service/connectors/sources/mongo/datasource.py
index 2fc9f70d3..0222f08ca 100644
--- a/app/connectors_service/connectors/sources/mongo/datasource.py
+++ b/app/connectors_service/connectors/sources/mongo/datasource.py
@@ -10,7 +10,14 @@
 from datetime import datetime
 from tempfile import NamedTemporaryFile
 
-from bson import OLD_UUID_SUBTYPE, Binary, DBRef, Decimal128, ObjectId
+from bson import (
+    OLD_UUID_SUBTYPE,
+    Binary,
+    DatetimeConversion,
+    DBRef,
+    Decimal128,
+    ObjectId,
+)
 from bson.binary import UUID_SUBTYPE
 from connectors_sdk.source import BaseDataSource, ConfigurableFieldValueError
 from motor.motor_asyncio import AsyncIOMotorClient
@@ -107,6 +114,11 @@ def get_client(self):
         try:
             client_params = {}
 
+            # Clamp out-of-range dates to datetime.min/max instead of raising,
+            # so extreme values stay valid dates and don't break the sync or
+            # the Elasticsearch date mapping.
+            client_params["datetime_conversion"] = DatetimeConversion.DATETIME_CLAMP
+
             if self.configuration["direct_connection"]:
                 client_params["directConnection"] = True
 
diff --git a/app/connectors_service/tests/sources/test_mongo.py b/app/connectors_service/tests/sources/test_mongo.py
index bcf0747ca..c171814ca 100644
--- a/app/connectors_service/tests/sources/test_mongo.py
+++ b/app/connectors_service/tests/sources/test_mongo.py
@@ -10,8 +10,10 @@
 from unittest.mock import AsyncMock, MagicMock, Mock
 from uuid import UUID
 
+import bson
 import pytest
-from bson import Binary, DBRef, ObjectId
+from bson import Binary, DatetimeConversion, DatetimeMS, DBRef, ObjectId
+from bson.codec_options import CodecOptions
 from bson.decimal128 import Decimal128
 from connectors_sdk.filtering.validation import Filter
 from connectors_sdk.source import ConfigurableFieldValueError
@@ -457,6 +459,20 @@ async def test_validate_config_when_configuration_valid_then_does_not_raise(
             },
             {"some_binary_uuid": None},
         ),
+        (
+            # in-range datetime serializes to an ISO string
+            {"created": datetime(2020, 1, 1, 12, 30, 0)},
+            {"created": "2020-01-01T12:30:00"},
+        ),
+        (
+            # dates clamped to the datetime bounds serialize to ISO strings too
+            {"clamped_max": datetime.max},
+            {"clamped_max": datetime.max.isoformat()},
+        ),
+        (
+            {"clamped_min": datetime.min},
+            {"clamped_min": datetime.min.isoformat()},
+        ),
     ],
 )
 async def test_serialize(raw, output):
@@ -464,6 +480,42 @@ async def test_serialize(raw, output):
         assert source.serialize(raw) == output
 
 
+@pytest.mark.asyncio
+async def test_get_client_clamps_out_of_range_dates():
+    async with create_mongo_source() as source:
+        with source.get_client() as client:
+            assert (
+                client.codec_options.datetime_conversion
+                == DatetimeConversion.DATETIME_CLAMP
+            )
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("milliseconds", [2**62, -(2**62), 0])
+async def test_out_of_range_dates_are_clamped_and_serialized_as_iso(milliseconds):
+    # An out-of-range BSON date (outside datetime's 1-9999 year range) must not
+    # abort the sync: the client clamps it to a valid datetime, which then
+    # serializes to an ISO string rather than a raw number.
+    async with create_mongo_source() as source:
+        with source.get_client() as client:
+            codec = client.codec_options
+
+        raw = bson.encode(
+            {"date": DatetimeMS(milliseconds)},
+            codec_options=CodecOptions(
+                datetime_conversion=DatetimeConversion.DATETIME_MS
+            ),
+        )
+        decoded = bson.decode(raw, codec_options=codec)
+
+        # Clamping yields a regular datetime, never a DatetimeMS.
+        assert isinstance(decoded["date"], datetime)
+
+        serialized = source.serialize(dict(decoded))
+        assert serialized["date"] == decoded["date"].isoformat()
+        assert isinstance(serialized["date"], str)
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize(
     "certificate_value, tls_insecure",