diff --git a/packages/aws-cdk-lib/aws-cloudwatch/lib/metric.ts b/packages/aws-cdk-lib/aws-cloudwatch/lib/metric.ts
index fc863f8f3787..99f7a27bc138 100644
--- a/packages/aws-cdk-lib/aws-cloudwatch/lib/metric.ts
+++ b/packages/aws-cdk-lib/aws-cloudwatch/lib/metric.ts
@@ -625,7 +625,7 @@ export class MathExpression implements IMetric {
     const missingIdentifiers = allIdentifiersInExpression(this.expression).filter(i => !this.usingMetrics[i]);
 
     const warnings: { [id: string]: string } = {};
-    if (!this.expression.toUpperCase().match('\\s*SELECT|SEARCH|METRICS\\s.*') && missingIdentifiers.length > 0) {
+    if (!this.expression.toUpperCase().match('\\s*INSIGHT_RULE_METRIC|SELECT|SEARCH|METRICS\\s.*') && missingIdentifiers.length > 0) {
       warnings['CloudWatch:Math:UnknownIdentifier'] = `Math expression '${this.expression}' references unknown identifiers: ${missingIdentifiers.join(', ')}. Please add them to the 'usingMetrics' map.`;
     }
 
diff --git a/packages/aws-cdk-lib/aws-cloudwatch/test/metric-math.test.ts b/packages/aws-cdk-lib/aws-cloudwatch/test/metric-math.test.ts
index 38d2bbd934a5..3b73f4193ddd 100644
--- a/packages/aws-cdk-lib/aws-cloudwatch/test/metric-math.test.ts
+++ b/packages/aws-cdk-lib/aws-cloudwatch/test/metric-math.test.ts
@@ -100,6 +100,15 @@ describe('Metric Math', () => {
     expect(m.warningsV2).toBeUndefined();
   });
 
+  test('metrics INSIGHT_RULE_METRIC expression does not produce warning for unknown identifier', () => {
+    const m = new MathExpression({
+      expression: "INSIGHT_RULE_METRIC('RejectedConnectionsRule', 'Sum')",
+      usingMetrics: {},
+    });
+
+    expect(m.warningsV2).toBeUndefined();
+  });
+
   test('math expression referring to unknown expressions produces a warning, even when nested', () => {
     const m = new MathExpression({
       expression: 'e1 + 5',