diff --git a/CHANGELOG.md b/CHANGELOG.md
index a65857c570..deb75167d6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Fixed
+
+- Add filtering term length check for channel filter endpoints @Ferril ([#3192](https://github.com/grafana/oncall/pull/3192))
+
 ## v1.3.46 (2023-10-23)
 
 ### Added
diff --git a/engine/apps/alerts/models/channel_filter.py b/engine/apps/alerts/models/channel_filter.py
index 2a9afdfee3..402560456b 100644
--- a/engine/apps/alerts/models/channel_filter.py
+++ b/engine/apps/alerts/models/channel_filter.py
@@ -76,7 +76,9 @@ class ChannelFilter(OrderedModel):
     notification_backends = models.JSONField(null=True, default=None)
 
     created_at = models.DateTimeField(auto_now_add=True)
-    filtering_term = models.CharField(max_length=1024, null=True, default=None)
+
+    FILTERING_TERM_MAX_LENGTH = 1024
+    filtering_term = models.CharField(max_length=FILTERING_TERM_MAX_LENGTH, null=True, default=None)
 
     FILTERING_TERM_TYPE_REGEX = 0
     FILTERING_TERM_TYPE_JINJA2 = 1
diff --git a/engine/apps/api/serializers/channel_filter.py b/engine/apps/api/serializers/channel_filter.py
index 17e92bbec9..b9239d6d48 100644
--- a/engine/apps/api/serializers/channel_filter.py
+++ b/engine/apps/api/serializers/channel_filter.py
@@ -60,6 +60,12 @@ class Meta:
     def validate(self, data):
         filtering_term = data.get("filtering_term")
         filtering_term_type = data.get("filtering_term_type")
+        if filtering_term is not None:
+            if len(filtering_term) > ChannelFilter.FILTERING_TERM_MAX_LENGTH:
+                raise serializers.ValidationError(
+                    f"Expression is too long. Maximum length: {ChannelFilter.FILTERING_TERM_MAX_LENGTH} characters, "
+                    f"current length: {len(filtering_term)}"
+                )
         if filtering_term_type == ChannelFilter.FILTERING_TERM_TYPE_JINJA2:
             try:
                 valid_jinja_template_for_serializer_method_field({"route_template": filtering_term})
@@ -141,7 +147,6 @@ def get_filtering_term_as_jinja2(self, obj):
 class ChannelFilterCreateSerializer(ChannelFilterSerializer):
     alert_receive_channel = OrganizationFilteredPrimaryKeyRelatedField(queryset=AlertReceiveChannel.objects)
     slack_channel = serializers.CharField(allow_null=True, required=False, source="slack_channel_id")
-    filtering_term = serializers.CharField(required=False, allow_null=True, allow_blank=True)
 
     class Meta:
         model = ChannelFilter
diff --git a/engine/apps/api/tests/test_channel_filter.py b/engine/apps/api/tests/test_channel_filter.py
index 31ab0a277e..2fd0944d94 100644
--- a/engine/apps/api/tests/test_channel_filter.py
+++ b/engine/apps/api/tests/test_channel_filter.py
@@ -552,3 +552,41 @@ def test_channel_filter_convert_from_regex_to_jinja2(
         assert jinja2_channel_filter.filtering_term == final_filtering_term
         # Check if the same alert is matched to the channel filter (route) new jinja2
         assert bool(jinja2_channel_filter.is_satisfying(payload)) is True
+
+
+@pytest.mark.django_db
+def test_channel_filter_long_filtering_term(
+    make_organization_and_user_with_plugin_token,
+    make_alert_receive_channel,
+    make_escalation_chain,
+    make_channel_filter,
+    make_user_auth_headers,
+):
+    organization, user, token = make_organization_and_user_with_plugin_token()
+    alert_receive_channel = make_alert_receive_channel(organization)
+    make_escalation_chain(organization)
+    make_channel_filter(alert_receive_channel, is_default=True)
+    client = APIClient()
+    long_filtering_term = "a" * (ChannelFilter.FILTERING_TERM_MAX_LENGTH + 1)
+
+    url = reverse("api-internal:channel_filter-list")
+    data_for_creation = {
+        "alert_receive_channel": alert_receive_channel.public_primary_key,
+        "filtering_term": long_filtering_term,
+    }
+
+    response = client.post(url, data=data_for_creation, format="json", **make_user_auth_headers(user, token))
+
+    assert response.status_code == status.HTTP_400_BAD_REQUEST
+    assert "Expression is too long" in response.json()["non_field_errors"][0]
+
+    channel_filter = make_channel_filter(alert_receive_channel, filtering_term="a", is_default=False)
+    url = reverse("api-internal:channel_filter-detail", kwargs={"pk": channel_filter.public_primary_key})
+    data_for_update = {
+        "filtering_term": long_filtering_term,
+    }
+
+    response = client.put(url, data=data_for_update, format="json", **make_user_auth_headers(user, token))
+
+    assert response.status_code == status.HTTP_400_BAD_REQUEST
+    assert "Expression is too long" in response.json()["non_field_errors"][0]
diff --git a/engine/apps/public_api/serializers/routes.py b/engine/apps/public_api/serializers/routes.py
index d680acf500..1907c9e9fc 100644
--- a/engine/apps/public_api/serializers/routes.py
+++ b/engine/apps/public_api/serializers/routes.py
@@ -163,8 +163,14 @@ def create(self, validated_data):
         return super().create(validated_data)
 
     def validate(self, data):
-        filtering_term = data.get("routing_regex")
-        filtering_term_type = data.get("routing_type")
+        filtering_term = data.get("filtering_term")
+        filtering_term_type = data.get("filtering_term_type")
+        if filtering_term is not None:
+            if len(filtering_term) > ChannelFilter.FILTERING_TERM_MAX_LENGTH:
+                raise serializers.ValidationError(
+                    f"Expression is too long. Maximum length: {ChannelFilter.FILTERING_TERM_MAX_LENGTH} characters, "
+                    f"current length: {len(filtering_term)}"
+                )
         if filtering_term_type == ChannelFilter.FILTERING_TERM_TYPE_JINJA2:
             try:
                 valid_jinja_template_for_serializer_method_field({"route_template": filtering_term})
diff --git a/engine/apps/public_api/tests/test_routes.py b/engine/apps/public_api/tests/test_routes.py
index 6aa8cdedb8..a03a238bdf 100644
--- a/engine/apps/public_api/tests/test_routes.py
+++ b/engine/apps/public_api/tests/test_routes.py
@@ -455,3 +455,36 @@ def test_update_route_with_manual_ordering(
 
     response = client.put(url, format="json", HTTP_AUTHORIZATION=token, data=data_to_update)
     assert response.status_code == status.HTTP_400_BAD_REQUEST
+
+
+@pytest.mark.django_db
+def test_routes_long_filtering_term(
+    route_public_api_setup,
+    make_channel_filter,
+):
+    organization, _, token, alert_receive_channel, escalation_chain, _ = route_public_api_setup
+    client = APIClient()
+    long_filtering_term = "a" * (ChannelFilter.FILTERING_TERM_MAX_LENGTH + 1)
+
+    url = reverse("api-public:routes-list")
+    data_for_creation = {
+        "integration_id": alert_receive_channel.public_primary_key,
+        "escalation_chain_id": escalation_chain.public_primary_key,
+        "routing_regex": long_filtering_term,
+    }
+
+    response = client.post(url, data=data_for_creation, format="json", HTTP_AUTHORIZATION=token)
+
+    assert response.status_code == status.HTTP_400_BAD_REQUEST
+    assert "Expression is too long" in response.json()["non_field_errors"][0]
+
+    channel_filter = make_channel_filter(alert_receive_channel, filtering_term="a", is_default=False)
+    url = reverse("api-public:routes-detail", kwargs={"pk": channel_filter.public_primary_key})
+    data_for_update = {
+        "routing_regex": long_filtering_term,
+    }
+
+    response = client.put(url, data=data_for_update, format="json", HTTP_AUTHORIZATION=token)
+
+    assert response.status_code == status.HTTP_400_BAD_REQUEST
+    assert "Expression is too long" in response.json()["non_field_errors"][0]