diff --git a/streetup/observations/templates/observations/observation_detail.html b/streetup/observations/templates/observations/observation_detail.html
index 21eab51..b999dda 100644
--- a/streetup/observations/templates/observations/observation_detail.html
+++ b/streetup/observations/templates/observations/observation_detail.html
@@ -497,6 +497,27 @@
                 </div>
                 <div class="card-body p-3 d-flex flex-column gap-3">
 
+                    {% if observation.intervention and observation.intervention.status == 'canceled' %}
+                    <div class="alert alert-warning d-flex align-items-center gap-2 mb-0" role="alert">
+                        <i class="bi bi-exclamation-triangle-fill text-warning fs-5 flex-shrink-0"></i>
+                        <div>
+                            <strong>{% translate "Attention :" %}</strong>
+                            {% translate "Une intervention liée à cette observation a été annulée" %}
+                            {% if observation.intervention.cancellation_type %}
+                                ({{ observation.intervention.get_cancellation_type_display }})
+                            {% endif %}
+                            :
+                            {% if can_view_intervention_detail %}
+                                <a href="{% url 'interventions:intervention_detail' observation.intervention.id %}" class="alert-link">
+                                    {{ observation.intervention.code }}
+                                </a>
+                            {% else %}
+                                <strong>{{ observation.intervention.code }}</strong>
+                            {% endif %}
+                        </div>
+                    </div>
+                    {% endif %}
+
                     {% if can_take_action and observation.status == 'to_process' %}
                     <!-- Deux colonnes : Intervention/Projet | Statut -->
                     <div class="d-flex flex-wrap gap-3 align-items-start">
diff --git a/streetup/observations/templates/observations/observation_detail_mobile.html b/streetup/observations/templates/observations/observation_detail_mobile.html
index 4628427..4f3dfe6 100644
--- a/streetup/observations/templates/observations/observation_detail_mobile.html
+++ b/streetup/observations/templates/observations/observation_detail_mobile.html
@@ -79,6 +79,27 @@
     </div>
     <div class="card-body p-3 d-flex flex-column gap-2">
 
+        {% if observation.intervention and observation.intervention.status == 'canceled' %}
+        <div class="alert alert-warning d-flex align-items-center gap-2 mb-2" role="alert">
+            <i class="bi bi-exclamation-triangle-fill text-warning fs-5 flex-shrink-0"></i>
+            <div class="small">
+                <strong>{% translate "Attention :" %}</strong>
+                {% translate "Une intervention liée à cette observation a été annulée" %}
+                {% if observation.intervention.cancellation_type %}
+                    ({{ observation.intervention.get_cancellation_type_display }})
+                {% endif %}
+                :
+                {% if can_view_intervention_detail %}
+                    <a href="{% url 'mobile:intervention_detail_mobile' observation.intervention.id %}" class="alert-link">
+                        {{ observation.intervention.code }}
+                    </a>
+                {% else %}
+                    <strong>{{ observation.intervention.code }}</strong>
+                {% endif %}
+            </div>
+        </div>
+        {% endif %}
+
         <!-- Deux colonnes : Intervention/Projet | Statut -->
         {% if observation.status == 'to_process' %}
             {% if can_take_action %}
diff --git a/streetup/observations/tests.py b/streetup/observations/tests.py
index 9117307..9c77fff 100644
--- a/streetup/observations/tests.py
+++ b/streetup/observations/tests.py
@@ -473,3 +473,32 @@ class ObservationPermissionTests(TestCase):
 		self.assertEqual(docs.count(), 1)
 		doc = docs.first()
 		self.assertEqual(doc.uploaded_by, self.internal_user)
+
+	def test_canceled_intervention_alert_on_observation_detail(self):
+		from interventions.models import Intervention
+		intervention = Intervention.objects.create(
+			code="INT-TEST-CANCEL",
+			title="Canceled intervention test",
+			status="canceled",
+			cancellation_type="duplicate",
+			thematic=self.thematic_a,
+			lat=50.5,
+			lon=4.5,
+		)
+		obs = Observation.objects.create(
+			description="Observation with canceled intervention",
+			latitude=50.5,
+			longitude=4.5,
+			created_by=self.internal_user,
+			thematic=self.thematic_a,
+			status="to_process",
+			intervention=intervention,
+		)
+
+		self.client.login(username="admin", password="pass")
+		detail_url = reverse("observations:observation_detail", args=[obs.id])
+		response = self.client.get(detail_url)
+		self.assertEqual(response.status_code, 200)
+		self.assertContains(response, "Une intervention liée à cette observation a été annulée")
+		self.assertContains(response, "INT-TEST-CANCEL")
+
diff --git a/streetup/observations/views.py b/streetup/observations/views.py
index 93ae179..d3adbc2 100644
--- a/streetup/observations/views.py
+++ b/streetup/observations/views.py
@@ -655,7 +655,7 @@ def observations_export_excel(request):
 
 
 @login_required
-@observation_object_permission_required()
+@observation_object_permission_required(select_related=('thematic', 'category', 'created_by', 'intervention', 'project'))
 def observation_detail(request, observation_id):
     """Detail page for a specific observation (desktop and mobile compatible)."""
     observation = request.observation_obj