diff --git a/rq_dashboard/web.py b/rq_dashboard/web.py
index dd41bdc..2f0fad7 100644
--- a/rq_dashboard/web.py
+++ b/rq_dashboard/web.py
@@ -40,7 +40,7 @@
     Worker,
     requeue_job,
 )
-from rq.exceptions import NoSuchJobError
+from rq.exceptions import DeserializationError, NoSuchJobError
 from rq.job import Job
 from rq.registry import (
     DeferredJobRegistry,
@@ -68,6 +68,27 @@ class Config:
 
 config: Config = Config()
 
+
+@blueprint.errorhandler(NoSuchJobError)
+def handle_no_such_job(exc):
+    """Return 404 so missing/expired jobs do not result in 500."""
+    return make_response(
+        json.dumps(dict(error="job_not_found")),
+        404,
+        {"Content-Type": "application/json", "Cache-Control": "no-store"},
+    )
+
+
+@blueprint.errorhandler(DeserializationError)
+def handle_deserialization_error(exc):
+    """Return 409 so corrupt job data does not result in 500."""
+    return make_response(
+        json.dumps(dict(error="job_deserialization_failed")),
+        409,
+        {"Content-Type": "application/json", "Cache-Control": "no-store"},
+    )
+
+
 # @blueprint.before_app_first_request
 def setup_rq_connection(current_app):
     # we need to do It here instead of cli, since It may be embeded
@@ -420,14 +441,8 @@ def job_view(instance_number, job_id):
 @check_delete_enable
 @jsonify
 def delete_job_view(job_id, registry=None):
-    try:
-        job = Job.fetch(job_id, connection=current_app.redis_conn)
-        job.delete()
-    except NoSuchJobError:
-        if registry:
-            registry.remove(job_id)
-        return dict(status="ERROR")
-
+    job = Job.fetch(job_id, connection=current_app.redis_conn)
+    job.delete()
     return dict(status="OK")
 
 
diff --git a/tests/test_basic.py b/tests/test_basic.py
index 757a165..a4b4f46 100644
--- a/tests/test_basic.py
+++ b/tests/test_basic.py
@@ -1,8 +1,10 @@
 import json
 import time
 import unittest
+from unittest.mock import patch
 
 import redis
+from rq.exceptions import DeserializationError, NoSuchJobError
 from rq import Queue, Worker
 
 from rq_dashboard.cli import make_flask_app
@@ -80,6 +82,34 @@ def some_work():
         response_del = self.client.post(job_del_url)
         self.assertEqual(response_del.status_code, HTTP_OK)
 
+    def test_delete_nonexistent_job_returns_404(self):
+        """Delete missing job returns 404 with job_not_found (not 500 or 200 ERROR)."""
+        response = self.client.post('/job/nonexistent-job-id/delete')
+        self.assertEqual(response.status_code, 404)
+        data = json.loads(response.data.decode('utf8'))
+        self.assertEqual(data, {'error': 'job_not_found'})
+
+    def test_view_nonexistent_job_returns_404(self):
+        """HTML job view for missing job returns 404."""
+        response = self.client.get('/0/view/job/nonexistent-job-id')
+        self.assertEqual(response.status_code, 404)
+
+    def test_job_info_nonexistent_returns_404(self):
+        """JSON job info for missing job returns 404 with job_not_found."""
+        response = self.client.get('/0/data/job/nonexistent-job-id.json')
+        self.assertEqual(response.status_code, 404)
+        data = json.loads(response.data.decode('utf8'))
+        self.assertEqual(data, {'error': 'job_not_found'})
+
+    def test_job_info_deserialization_error_returns_409(self):
+        """Corrupt job data returns 409 with job_deserialization_failed."""
+        with patch('rq_dashboard.web.Job') as mock_job:
+            mock_job.fetch.side_effect = DeserializationError()
+            response = self.client.get('/0/data/job/any-id.json')
+        self.assertEqual(response.status_code, 409)
+        data = json.loads(response.data.decode('utf8'))
+        self.assertEqual(data, {'error': 'job_deserialization_failed'})
+
     def test_registry_jobs_list(self):
         for registry_name in REGISTRY_NAMES:
             response = self.client.get(f'/0/data/jobs/default/{registry_name}/8/asc/1.json')