diff --git a/superset/sqllab/api.py b/superset/sqllab/api.py
index 5b6d585f9c7..62e5a683cb3 100644
--- a/superset/sqllab/api.py
+++ b/superset/sqllab/api.py
@@ -23,6 +23,7 @@ from flask import current_app as app, request, Response
 from flask_appbuilder import permission_name
 from flask_appbuilder.api import expose, protect, rison as parse_rison, safe
 from flask_appbuilder.models.sqla.interface import SQLAInterface
+from jinja2.exceptions import TemplateError
 from marshmallow import ValidationError
 from werkzeug.utils import secure_filename
 
@@ -37,6 +38,8 @@ from superset.commands.sql_lab.streaming_export_command import (
 from superset.constants import MODEL_API_RW_METHOD_PERMISSION_MAP
 from superset.daos.database import DatabaseDAO
 from superset.daos.query import QueryDAO
+from superset.errors import ErrorLevel, SupersetError, SupersetErrorType
+from superset.exceptions import SupersetErrorException
 from superset.extensions import event_logger, security_manager
 from superset.jinja_context import get_template_processor
 from superset.models.sql_lab import Query
@@ -266,6 +269,15 @@ class SqlLabRestApi(BaseSupersetApi):
                                 "Invalid template parameter %s. Skipping processing",
                                 str(template_params),
                             )
+                        except TemplateError as ex:
+                            raise SupersetErrorException(
+                                SupersetError(
+                                    message=str(ex),
+                                    error_type=SupersetErrorType.GENERIC_COMMAND_ERROR,
+                                    level=ErrorLevel.ERROR,
+                                ),
+                                status=400,
+                            ) from ex
 
             result = SQLScript(sql, model.get("engine", database_engine)).format()
             return self.response(200, result=result)
diff --git a/tests/integration_tests/sql_lab/api_tests.py b/tests/integration_tests/sql_lab/api_tests.py
index 4329946fe89..4527112000c 100644
--- a/tests/integration_tests/sql_lab/api_tests.py
+++ b/tests/integration_tests/sql_lab/api_tests.py
@@ -336,6 +336,29 @@ class TestSqlLabApi(SupersetTestCase):
         assert "{{tbl}}" not in resp_data["result"]
         assert resp_data["result"] == expected
 
+    def test_format_sql_request_with_undefined_jinja_attribute(self):
+        self.login(ADMIN_USERNAME)
+        example_db = get_example_database()
+
+        # Attribute access on an undefined Jinja variable (``tbl`` is not in the
+        # template params) raises a jinja2 ``UndefinedError`` from within
+        # ``process_template``. This should surface as a typed 400, not an opaque
+        # 500 from the global exception handler. A non-empty ``template_params``
+        # dict is required so the endpoint actually invokes ``process_template``.
+        data = {
+            "sql": "select * from {{ tbl.name }}",
+            "database_id": example_db.id,
+            "template_params": json.dumps({"unrelated": "value"}),
+        }
+        rv = self.client.post(
+            "/api/v1/sqllab/format_sql/",
+            json=data,
+        )
+        resp_data = json.loads(rv.data.decode("utf-8"))
+        assert rv.status_code == 400
+        assert "tbl" in resp_data["errors"][0]["message"]
+        assert "undefined" in resp_data["errors"][0]["message"]
+
     @mock.patch("superset.commands.sql_lab.results.results_backend_use_msgpack", False)
     def test_execute_required_params(self):
         self.login(ADMIN_USERNAME)