diff --git a/elementary/monitor/data_monitoring/report/data_monitoring_report.py b/elementary/monitor/data_monitoring/report/data_monitoring_report.py
index 7493b96e7..32b920ace 100644
--- a/elementary/monitor/data_monitoring/report/data_monitoring_report.py
+++ b/elementary/monitor/data_monitoring/report/data_monitoring_report.py
@@ -8,7 +8,7 @@
 from elementary.clients.azure.client import AzureClient
 from elementary.clients.gcs.client import GCSClient
 from elementary.clients.s3.client import S3Client
-from elementary.clients.slack.client import SlackClient
+from elementary.clients.slack.client import SlackClient, SlackWebhookClient
 from elementary.config.config import Config
 from elementary.monitor.api.invocations.invocations import InvocationsAPI
 from elementary.monitor.api.report.report import ReportAPI
@@ -227,7 +227,14 @@ def send_report(
             )
             if should_send_report_over_slack:
                 self.validate_report_selector()
-                self.send_report_attachment(local_html_path=local_html_path)
+                if isinstance(self.slack_client, SlackWebhookClient):
+                    # Slack webhooks can only post messages, not upload files.
+                    logger.warning(
+                        "Skipping the report attachment: a Slack webhook cannot upload files. "
+                        "Use a Slack token or a bucket website to share the report."
+                    )
+                else:
+                    self.send_report_attachment(local_html_path=local_html_path)
 
         return self.success
 
diff --git a/tests/unit/monitor/data_monitoring/report/test_data_monitoring_report.py b/tests/unit/monitor/data_monitoring/report/test_data_monitoring_report.py
new file mode 100644
index 000000000..fa42ee849
--- /dev/null
+++ b/tests/unit/monitor/data_monitoring/report/test_data_monitoring_report.py
@@ -0,0 +1,77 @@
+from typing import Optional
+from unittest.mock import MagicMock
+
+import pytest
+
+from elementary.clients.slack.client import SlackWebClient, SlackWebhookClient
+from elementary.config.config import Config
+from elementary.monitor.data_monitoring.report.data_monitoring_report import (
+    DataMonitoringReport,
+)
+from tests.mocks.dbt_runner_mock import MockDbtRunner
+
+LOCAL_REPORT_PATH = "/tmp/elementary_report.html"
+
+
+class DataMonitoringReportMock(DataMonitoringReport):
+    def __init__(self, config: Config, bucket_website_url: Optional[str] = None):
+        super().__init__(config=config, tracking=None)
+        # Stand-ins for the parts of send_report that need a warehouse or a bucket.
+        self.generate_report = MagicMock(return_value=(True, LOCAL_REPORT_PATH))
+        self.send_test_results_summary = MagicMock(return_value=True)
+        self.s3_client = MagicMock()
+        self.s3_client.send_report.return_value = (True, bucket_website_url)
+
+    def _init_internal_dbt_runner(self):
+        return MockDbtRunner()
+
+    def get_latest_invocation(self):
+        return dict()
+
+    def _get_warehouse_info(self, *args, **kwargs):
+        return None
+
+    def get_elementary_database_and_schema(self):
+        return "<elementary_database>.<elementary_schema>"
+
+
+@pytest.fixture
+def webhook_and_s3_config(tmp_path) -> Config:
+    return Config(
+        config_dir=str(tmp_path / "config"),
+        target_path=str(tmp_path / "target"),
+        slack_webhook="https://hooks.slack.com/services/T000/B000/XXXX",
+        s3_bucket_name="elementary-reports",
+    )
+
+
+def test_send_report_with_slack_webhook_skips_html_attachment(
+    webhook_and_s3_config: Config,
+):
+    report = DataMonitoringReportMock(webhook_and_s3_config)
+    assert isinstance(report.slack_client, SlackWebhookClient)
+
+    assert report.send_report() is True
+
+    report.s3_client.send_report.assert_called_once()
+    report.send_test_results_summary.assert_called_once()
+    assert report.success is True
+
+
+def test_send_report_with_slack_token_still_sends_html_attachment(tmp_path):
+    config = Config(
+        config_dir=str(tmp_path / "config"),
+        target_path=str(tmp_path / "target"),
+        slack_token="xoxb-mock",
+        slack_channel_name="data-reports",
+        s3_bucket_name="elementary-reports",
+    )
+    report = DataMonitoringReportMock(config)
+    assert isinstance(report.slack_client, SlackWebClient)
+    report.slack_client.send_report = MagicMock(return_value=True)
+
+    assert report.send_report() is True
+
+    report.slack_client.send_report.assert_called_once_with(
+        "data-reports", LOCAL_REPORT_PATH
+    )