diff --git a/litellm/integrations/prometheus.py b/litellm/integrations/prometheus.py
index 357e0229fc..90306c11a4 100644
--- a/litellm/integrations/prometheus.py
+++ b/litellm/integrations/prometheus.py
@@ -931,10 +931,14 @@ class PrometheusLogger(CustomLogger):
         user_api_key_auth_metadata: Optional[dict] = standard_logging_payload[
             "metadata"
         ].get("user_api_key_auth_metadata")
+        spend_logs_metadata: Optional[dict] = standard_logging_payload["metadata"].get(
+            "spend_logs_metadata"
+        )
 
         combined_metadata: Dict[str, Any] = {
             **(_requester_metadata if _requester_metadata else {}),
             **(user_api_key_auth_metadata if user_api_key_auth_metadata else {}),
+            **(spend_logs_metadata if spend_logs_metadata else {}),
         }
         if standard_logging_payload is not None and isinstance(
             standard_logging_payload, dict
diff --git a/tests/test_litellm/integrations/test_prometheus_spend_logs_metadata.py b/tests/test_litellm/integrations/test_prometheus_spend_logs_metadata.py
new file mode 100644
index 0000000000..d60c2ae929
--- /dev/null
+++ b/tests/test_litellm/integrations/test_prometheus_spend_logs_metadata.py
@@ -0,0 +1,110 @@
+"""
+Unit tests for spend_logs_metadata inclusion in Prometheus custom labels.
+
+Verifies that metadata from x-litellm-spend-logs-metadata header is available
+in Prometheus custom labels via combined_metadata.
+"""
+from litellm.integrations.prometheus import get_custom_labels_from_metadata
+
+
+def test_get_custom_labels_includes_spend_logs_metadata(monkeypatch):
+    """
+    Test that get_custom_labels_from_metadata extracts fields from
+    spend_logs_metadata when it is merged into combined_metadata.
+    """
+    monkeypatch.setattr(
+        "litellm.custom_prometheus_metadata_labels",
+        ["metadata.department", "metadata.env"],
+    )
+
+    # Simulate combined_metadata after merging all three sources
+    combined_metadata = {
+        "request_key": "from_requester",  # from requester_metadata
+        "auth_key": "from_auth",  # from user_api_key_auth_metadata
+        "department": "engineering",  # from spend_logs_metadata
+        "env": "production",  # from spend_logs_metadata
+    }
+
+    result = get_custom_labels_from_metadata(combined_metadata)
+    assert result == {
+        "metadata_department": "engineering",
+        "metadata_env": "production",
+    }
+
+
+def test_spend_logs_metadata_overrides_earlier_sources(monkeypatch):
+    """
+    Test that spend_logs_metadata values take precedence over
+    requester_metadata and user_api_key_auth_metadata when keys overlap,
+    since it is spread last in combined_metadata.
+    """
+    monkeypatch.setattr(
+        "litellm.custom_prometheus_metadata_labels",
+        ["metadata.team"],
+    )
+
+    # Simulate the dict spread order: requester -> auth -> spend_logs
+    requester_metadata = {"team": "old_team"}
+    user_api_key_auth_metadata = {"team": "auth_team"}
+    spend_logs_metadata = {"team": "spend_team"}
+
+    combined_metadata = {
+        **requester_metadata,
+        **user_api_key_auth_metadata,
+        **spend_logs_metadata,
+    }
+
+    result = get_custom_labels_from_metadata(combined_metadata)
+    assert result == {"metadata_team": "spend_team"}
+
+
+def test_combined_metadata_with_all_three_sources(monkeypatch):
+    """
+    Test that combined_metadata correctly merges requester_metadata,
+    user_api_key_auth_metadata, and spend_logs_metadata.
+    """
+    monkeypatch.setattr(
+        "litellm.custom_prometheus_metadata_labels",
+        ["metadata.from_requester", "metadata.from_auth", "metadata.from_spend"],
+    )
+
+    # Reproduce the exact spread pattern from prometheus.py
+    _requester_metadata = {"from_requester": "val1"}
+    user_api_key_auth_metadata = {"from_auth": "val2"}
+    spend_logs_metadata = {"from_spend": "val3"}
+
+    combined_metadata = {
+        **(_requester_metadata if _requester_metadata else {}),
+        **(user_api_key_auth_metadata if user_api_key_auth_metadata else {}),
+        **(spend_logs_metadata if spend_logs_metadata else {}),
+    }
+
+    result = get_custom_labels_from_metadata(combined_metadata)
+    assert result == {
+        "metadata_from_requester": "val1",
+        "metadata_from_auth": "val2",
+        "metadata_from_spend": "val3",
+    }
+
+
+def test_combined_metadata_with_none_spend_logs(monkeypatch):
+    """
+    Test that combined_metadata works when spend_logs_metadata is None.
+    """
+    monkeypatch.setattr(
+        "litellm.custom_prometheus_metadata_labels",
+        ["metadata.foo"],
+    )
+
+    _requester_metadata = {"foo": "bar"}
+    user_api_key_auth_metadata = None
+    spend_logs_metadata = None
+
+    combined_metadata = {
+        **(_requester_metadata if _requester_metadata else {}),
+        **(user_api_key_auth_metadata if user_api_key_auth_metadata else {}),
+        **(spend_logs_metadata if spend_logs_metadata else {}),
+    }
+
+    result = get_custom_labels_from_metadata(combined_metadata)
+    assert result == {"metadata_foo": "bar"}