diff --git a/src/databricks/sql/client.py b/src/databricks/sql/client.py
index 1a246b7c1..266c6eff4 100755
--- a/src/databricks/sql/client.py
+++ b/src/databricks/sql/client.py
@@ -93,6 +93,78 @@
 # Transaction isolation level constants (extension to PEP 249)
 TRANSACTION_ISOLATION_LEVEL_REPEATABLE_READ = "REPEATABLE_READ"
 
+# All supported **kwargs for Connection.__init__. Used to warn on unknown params.
+KNOWN_KWARGS = frozenset(
+    [
+        # Authentication
+        "access_token",
+        "auth_type",
+        "username",
+        "password",
+        "credentials_provider",
+        "_use_cert_as_auth",
+        "oauth_client_id",
+        "oauth_redirect_port",
+        "oauth_scopes",
+        "experimental_oauth_persistence",
+        "identity_federation_client_id",
+        "azure_client_id",
+        "azure_client_secret",
+        "azure_tenant_id",
+        "azure_workspace_resource_id",
+        # TLS / SSL
+        "_enable_ssl",
+        "_tls_no_verify",
+        "_tls_verify_hostname",
+        "_tls_trusted_ca_file",
+        "_tls_client_cert_file",
+        "_tls_client_cert_key_file",
+        "_tls_client_cert_key_password",
+        # Connection
+        "_port",
+        "_connection_uri",
+        "_skip_routing_headers",
+        # Retry policy
+        "_retry_delay_min",
+        "_retry_delay_max",
+        "_retry_delay_default",
+        "_retry_stop_after_attempts_count",
+        "_retry_stop_after_attempts_duration",
+        "_retry_dangerous_codes",
+        "_retry_max_redirects",
+        "_enable_v3_retries",
+        # Socket / network
+        "_socket_timeout",
+        "_proxy_auth_method",
+        "_pool_connections",
+        "_pool_maxsize",
+        "pool_maxsize",
+        # User agent & telemetry
+        "user_agent_entry",
+        "_user_agent_entry",
+        "enable_telemetry",
+        "force_enable_telemetry",
+        "telemetry_batch_size",
+        "_telemetry_circuit_breaker_enabled",
+        # Query / result
+        "use_inline_params",
+        "enable_query_result_lz4_compression",
+        "use_cloud_fetch",
+        "max_download_threads",
+        "use_hybrid_disposition",
+        "staging_allowed_local_path",
+        # Data type / format
+        "_use_arrow_native_decimals",
+        "_use_arrow_native_timestamps",
+        "_disable_pandas",
+        # Behavior
+        "enable_metric_view_metadata",
+        "fetch_autocommit_from_server",
+        # Backend selection
+        "use_sea",
+    ]
+)
+
 
 class Connection:
     def __init__(
@@ -269,6 +341,14 @@ def read(self) -> Optional[OAuthToken]:
             http_path,
         )
 
+        unknown_params = set(kwargs.keys()) - KNOWN_KWARGS
+        if unknown_params:
+            logger.warning(
+                "Unsupported connection parameter(s) will be ignored: %s. "
+                "Check the Connection documentation for supported parameters.",
+                ", ".join(sorted(unknown_params)),
+            )
+
         if access_token:
             access_token_kv = {"access_token": access_token}
             kwargs = {**kwargs, **access_token_kv}
diff --git a/tests/unit/test_client.py b/tests/unit/test_client.py
index 5b6991931..ece617c21 100644
--- a/tests/unit/test_client.py
+++ b/tests/unit/test_client.py
@@ -633,6 +633,61 @@ def mock_close_normal():
             cursors_closed, [1, 2], "Both cursors should have close called"
         )
 
+    @patch("%s.session.ThriftDatabricksClient" % PACKAGE_NAME)
+    @patch("databricks.sql.client.logger")
+    def test_unknown_connection_param_issues_warning(
+        self, mock_logger, mock_client_class
+    ):
+        """Unknown kwargs passed to Connection should trigger a warning."""
+        databricks.sql.connect(
+            **self.DUMMY_CONNECTION_ARGS, totally_unknown_param="value"
+        )
+        mock_logger.warning.assert_called_once()
+        warning_msg = mock_logger.warning.call_args[0][0]
+        self.assertIn("Unsupported connection parameter", warning_msg)
+
+    @patch("%s.session.ThriftDatabricksClient" % PACKAGE_NAME)
+    @patch("databricks.sql.client.logger")
+    def test_unknown_connection_param_warning_names_the_param(
+        self, mock_logger, mock_client_class
+    ):
+        """Warning message should include the name of the unknown parameter."""
+        databricks.sql.connect(
+            **self.DUMMY_CONNECTION_ARGS, totally_unknown_param="value"
+        )
+        # The unknown param name should appear in the warning args
+        call_args = mock_logger.warning.call_args
+        formatted_msg = call_args[0][0] % call_args[0][1:]
+        self.assertIn("totally_unknown_param", formatted_msg)
+
+    @patch("%s.session.ThriftDatabricksClient" % PACKAGE_NAME)
+    @patch("databricks.sql.client.logger")
+    def test_known_connection_params_do_not_issue_warning(
+        self, mock_logger, mock_client_class
+    ):
+        """Known kwargs passed to Connection should not trigger an unknown-param warning."""
+        databricks.sql.connect(**self.DUMMY_CONNECTION_ARGS, use_cloud_fetch=False)
+        for call in mock_logger.warning.call_args_list:
+            msg = call[0][0]
+            self.assertNotIn("Unsupported connection parameter", msg)
+
+    @patch("%s.session.ThriftDatabricksClient" % PACKAGE_NAME)
+    @patch("databricks.sql.client.logger")
+    def test_multiple_unknown_params_all_appear_in_warning(
+        self, mock_logger, mock_client_class
+    ):
+        """All unknown param names should appear in the warning message."""
+        databricks.sql.connect(
+            **self.DUMMY_CONNECTION_ARGS,
+            bad_param_one="a",
+            bad_param_two="b",
+        )
+        mock_logger.warning.assert_called_once()
+        call_args = mock_logger.warning.call_args
+        formatted_msg = call_args[0][0] % call_args[0][1:]
+        self.assertIn("bad_param_one", formatted_msg)
+        self.assertIn("bad_param_two", formatted_msg)
+
 
 class TransactionTestSuite(unittest.TestCase):
     """