diff --git a/pkg/controller/podautoscaler/replica_calculator.go b/pkg/controller/podautoscaler/replica_calculator.go
index 49f68ae0c4e..00ae980d47a 100644
--- a/pkg/controller/podautoscaler/replica_calculator.go
+++ b/pkg/controller/podautoscaler/replica_calculator.go
@@ -360,8 +360,14 @@ func (c *ReplicaCalculator) GetExternalMetricReplicas(currentReplicas int32, tar
 	if err != nil {
 		return 0, 0, time.Time{}, fmt.Errorf("unable to get external metric %s/%s/%+v: %s", namespace, metricName, metricSelector, err)
 	}
+
 	usage = 0
 	for _, val := range metrics {
+		// Cap at MaxInt64 for positive overflow
+		if val > 0 && usage > math.MaxInt64-val {
+			usage = math.MaxInt64
+			break
+		}
 		usage = usage + val
 	}
 
diff --git a/pkg/controller/podautoscaler/replica_calculator_test.go b/pkg/controller/podautoscaler/replica_calculator_test.go
index 202bce959d4..bd8755fb56c 100644
--- a/pkg/controller/podautoscaler/replica_calculator_test.go
+++ b/pkg/controller/podautoscaler/replica_calculator_test.go
@@ -2477,3 +2477,21 @@ func TestCalculatePodRequestsFromContainers_NonExistentContainer(t *testing.T) {
 	assert.Equal(t, expectedErr, err.Error(), "error message should match expected format")
 	assert.Equal(t, int64(0), request, "request should be 0 when container does not exist")
 }
+
+func TestReplicaCalcExternalMetricUsageOverflow(t *testing.T) {
+	tc := replicaCalcTestCase{
+		currentReplicas:  3,
+		expectedReplicas: 3,
+		metric: &metricInfo{
+			name: "qps",
+			// Two values that when added together will overflow int64
+			levels:        []int64{math.MaxInt64/2 + 1, math.MaxInt64/2 + 1},
+			targetUsage:   math.MaxInt64, // Set high target
+			metricType:    externalMetric,
+			selector:      &metav1.LabelSelector{MatchLabels: map[string]string{"label": "value"}},
+			expectedUsage: math.MaxInt64, // expect capped value
+
+		},
+	}
+	tc.runTest(t)
+}