diff --git a/backend/app/services/test_workflow_service.py b/backend/app/services/test_workflow_service.py
index 361d2fd..f26357e 100644
--- a/backend/app/services/test_workflow_service.py
+++ b/backend/app/services/test_workflow_service.py
@@ -20,7 +20,8 @@ from sqlalchemy.orm import Session
 from app.config import settings
 from app.domain.exceptions import InvalidOperationError, InvalidTransitionError
 from app.domain.test_entity import TestEntity
-from app.models.enums import TestState
+from app.models.enums import TestState, TeamSide
+from app.models.evidence import Evidence
 from app.models.test import Test
 from app.models.user import User
 from app.services.audit_service import log_action
@@ -146,9 +147,21 @@ def submit_red_evidence(db: Session, test: Test, user: User) -> Test:
     """Move from ``red_executing`` → ``blue_evaluating``.
 
     Called by **red_tech** once they have finished documenting the attack.
+    Requires at least one Red Team evidence file to be uploaded.
     Stops the Red Team timer and creates an automatic worklog.
     Starts the Blue Team timer by recording ``blue_started_at``.
     """
+    # Evidence is mandatory before submitting
+    red_evidence_count = (
+        db.query(Evidence)
+        .filter(Evidence.test_id == test.id, Evidence.team == TeamSide.red)
+        .count()
+    )
+    if red_evidence_count == 0:
+        raise InvalidOperationError(
+            "Cannot submit to Blue Team: at least one Red Team evidence file must be uploaded first."
+        )
+
     now = datetime.utcnow()
 
     # Auto-resume if paused
@@ -224,10 +237,22 @@ def submit_blue_evidence(db: Session, test: Test, user: User) -> Test:
     """Move from ``blue_evaluating`` → ``in_review``.
 
     Called by **blue_tech** once they have finished documenting detection.
+    Requires at least one Blue Team evidence file to be uploaded.
     Stops the Blue Team timer and creates an automatic worklog.
     Uses blue_work_started_at as the phase start for Tempo if available,
     otherwise falls back to blue_started_at (queue-entry timestamp).
     """
+    # Evidence is mandatory before submitting
+    blue_evidence_count = (
+        db.query(Evidence)
+        .filter(Evidence.test_id == test.id, Evidence.team == TeamSide.blue)
+        .count()
+    )
+    if blue_evidence_count == 0:
+        raise InvalidOperationError(
+            "Cannot submit for review: at least one Blue Team evidence file must be uploaded first."
+        )
+
     now = datetime.utcnow()
 
     # Auto-resume if paused
diff --git a/frontend/src/components/test-detail/TestDetailHeader.tsx b/frontend/src/components/test-detail/TestDetailHeader.tsx
index 42df425..a6151f7 100644
--- a/frontend/src/components/test-detail/TestDetailHeader.tsx
+++ b/frontend/src/components/test-detail/TestDetailHeader.tsx
@@ -111,21 +111,27 @@ export default function TestDetailHeader({
       );
     }
 
-    // Red Team in red_executing -> Submit to Blue Team
+    // Red Team in red_executing -> Submit to Blue Team (requires ≥1 red evidence)
     if (
       test.state === "red_executing" &&
       (role === "red_tech" || role === "red_lead" || role === "admin")
     ) {
+      const hasRedEvidence = (test.red_evidences?.length ?? 0) > 0;
       buttons.push(
-        <button
-          key="submit-red"
-          onClick={onSubmitRed}
-          disabled={isTransitioning}
-          className="flex items-center gap-1.5 rounded-lg bg-indigo-600 px-4 py-2 text-sm font-medium text-white hover:bg-indigo-500 transition-colors disabled:opacity-50"
-        >
-          {isTransitioning ? <Loader2 className="h-4 w-4 animate-spin" /> : <Send className="h-4 w-4" />}
-          Submit to Blue Team
-        </button>,
+        <div key="submit-red" className="flex flex-col items-end gap-1">
+          <button
+            onClick={onSubmitRed}
+            disabled={isTransitioning || !hasRedEvidence}
+            title={!hasRedEvidence ? "Upload at least one Red Team evidence file before submitting" : undefined}
+            className="flex items-center gap-1.5 rounded-lg bg-indigo-600 px-4 py-2 text-sm font-medium text-white hover:bg-indigo-500 transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
+          >
+            {isTransitioning ? <Loader2 className="h-4 w-4 animate-spin" /> : <Send className="h-4 w-4" />}
+            Submit to Blue Team
+          </button>
+          {!hasRedEvidence && (
+            <span className="text-[10px] text-orange-400">⚠ Upload evidence first</span>
+          )}
+        </div>,
       );
     }
 
@@ -149,16 +155,23 @@ export default function TestDetailHeader({
           </button>,
         );
       } else {
+        // Submit for Review requires ≥1 blue evidence
+        const hasBlueEvidence = (test.blue_evidences?.length ?? 0) > 0;
         buttons.push(
-          <button
-            key="submit-blue"
-            onClick={onSubmitBlue}
-            disabled={isTransitioning}
-            className="flex items-center gap-1.5 rounded-lg bg-blue-600 px-4 py-2 text-sm font-medium text-white hover:bg-blue-500 transition-colors disabled:opacity-50"
-          >
-            {isTransitioning ? <Loader2 className="h-4 w-4 animate-spin" /> : <Send className="h-4 w-4" />}
-            Submit for Review
-          </button>,
+          <div key="submit-blue" className="flex flex-col items-end gap-1">
+            <button
+              onClick={onSubmitBlue}
+              disabled={isTransitioning || !hasBlueEvidence}
+              title={!hasBlueEvidence ? "Upload at least one Blue Team evidence file before submitting" : undefined}
+              className="flex items-center gap-1.5 rounded-lg bg-blue-600 px-4 py-2 text-sm font-medium text-white hover:bg-blue-500 transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
+            >
+              {isTransitioning ? <Loader2 className="h-4 w-4 animate-spin" /> : <Send className="h-4 w-4" />}
+              Submit for Review
+            </button>
+            {!hasBlueEvidence && (
+              <span className="text-[10px] text-orange-400">⚠ Upload evidence first</span>
+            )}
+          </div>,
         );
       }
     }