diff --git a/packages/system/monitoring/templates/_helpers.tpl b/packages/system/monitoring/templates/_helpers.tpl
index 59d8ba714..389720959 100644
--- a/packages/system/monitoring/templates/_helpers.tpl
+++ b/packages/system/monitoring/templates/_helpers.tpl
@@ -327,3 +327,12 @@
 {{- define "monitoring.tracingCentral" -}}
 {{- if and (ne .Release.Namespace "tenant-root") (eq (toString (dig "tracingCentral" false (.Values._namespace | default dict))) "true") -}}true{{- end -}}
 {{- end -}}
+
+{{- /*
+  Alertmanager replica count. vmalert lists each replica as its own
+  notifier from the same number, because the Alertmanager cluster only
+  deduplicates notifications when every replica receives every alert.
+*/}}
+{{- define "monitoring.alertmanager.replicas" -}}
+3
+{{- end -}}
diff --git a/packages/system/monitoring/templates/alerta/alerta.yaml b/packages/system/monitoring/templates/alerta/alerta.yaml
index c6becd1bd..6376eaa9e 100644
--- a/packages/system/monitoring/templates/alerta/alerta.yaml
+++ b/packages/system/monitoring/templates/alerta/alerta.yaml
@@ -419,7 +419,7 @@ spec:
       apps.cozystack.io/application.group: apps.cozystack.io
       apps.cozystack.io/application.kind: Monitoring
       apps.cozystack.io/application.name: {{ $.Release.Name }}
-  replicaCount: 3
+  replicaCount: {{ include "monitoring.alertmanager.replicas" $ }}
   configSecret: alertmanager
   {{- if and $emailEnabled $email.authUsername }}
   secrets:
diff --git a/packages/system/monitoring/templates/vm/vmalert.yaml b/packages/system/monitoring/templates/vm/vmalert.yaml
index 8da03e152..b4f0c8aa1 100644
--- a/packages/system/monitoring/templates/vm/vmalert.yaml
+++ b/packages/system/monitoring/templates/vm/vmalert.yaml
@@ -16,7 +16,9 @@ spec:
   extraArgs:
     remoteWrite.disablePathAppend: "true"
   notifiers:
-  - url: http://vmalertmanager-alertmanager.{{ $.Release.Namespace }}.svc:9093
+  {{- range $i := until (int (include "monitoring.alertmanager.replicas" $)) }}
+  - url: http://vmalertmanager-alertmanager-{{ $i }}.vmalertmanager-alertmanager.{{ $.Release.Namespace }}.svc:9093
+  {{- end }}
   remoteRead:
     url: http://vmselect-{{ .name }}.{{ $.Release.Namespace }}.svc:8481/select/0/prometheus
   remoteWrite:
diff --git a/packages/system/monitoring/tests/vmalert_notifiers_test.yaml b/packages/system/monitoring/tests/vmalert_notifiers_test.yaml
new file mode 100644
index 000000000..6133b1f55
--- /dev/null
+++ b/packages/system/monitoring/tests/vmalert_notifiers_test.yaml
@@ -0,0 +1,55 @@
+suite: vmalert notifies every Alertmanager replica
+templates:
+  - templates/vm/vmalert.yaml
+  - templates/alerta/alerta.yaml
+
+release:
+  name: monitoring
+  namespace: tenant-root
+
+set:
+  _cluster:
+    root-host: example.org
+  _namespace:
+    host: tenant-root.example.org
+    ingress: tenant-root
+  metricsStorages:
+    - name: shortterm
+      retentionPeriod: "3d"
+      deduplicationInterval: "15s"
+
+# The Alertmanager cluster deduplicates notifications only when every replica
+# receives every alert. A notifier pointing at the headless Service reaches
+# one pod per connection, so an alert lives on whichever replica that
+# connection landed on and moves when vmalert reconnects. Each replica it
+# leaves sends a resolved notification and each one it reaches sends a new
+# firing one.
+tests:
+  - it: lists each Alertmanager pod as a notifier instead of the shared Service
+    template: templates/vm/vmalert.yaml
+    asserts:
+      - equal:
+          path: spec.notifiers
+          value:
+            - url: http://vmalertmanager-alertmanager-0.vmalertmanager-alertmanager.tenant-root.svc:9093
+            - url: http://vmalertmanager-alertmanager-1.vmalertmanager-alertmanager.tenant-root.svc:9093
+            - url: http://vmalertmanager-alertmanager-2.vmalertmanager-alertmanager.tenant-root.svc:9093
+
+  - it: runs as many Alertmanager replicas as vmalert has notifiers
+    template: templates/alerta/alerta.yaml
+    documentSelector:
+      path: kind
+      value: VMAlertmanager
+    asserts:
+      - equal:
+          path: spec.replicaCount
+          value: 3
+
+  - it: addresses the Alertmanager pods in the release namespace
+    template: templates/vm/vmalert.yaml
+    release:
+      namespace: tenant-foo
+    asserts:
+      - equal:
+          path: spec.notifiers[2].url
+          value: http://vmalertmanager-alertmanager-2.vmalertmanager-alertmanager.tenant-foo.svc:9093