diff --git a/packages/@aws-cdk-testing/cli-integ/lib/package-sources/repo-source.ts b/packages/@aws-cdk-testing/cli-integ/lib/package-sources/repo-source.ts
index 45a8f4e5d4dfc..7a5f08ec71b98 100644
--- a/packages/@aws-cdk-testing/cli-integ/lib/package-sources/repo-source.ts
+++ b/packages/@aws-cdk-testing/cli-integ/lib/package-sources/repo-source.ts
@@ -75,13 +75,14 @@ const YARN_MONOREPO_CACHE: Record<string, any> = {};
   *
   * Cached in YARN_MONOREPO_CACHE.
   */
-async function findYarnPackages(root: string): Promise<Record<string, string>> {
+export async function findYarnPackages(root: string): Promise<Record<string, string>> {
   if (!(root in YARN_MONOREPO_CACHE)) {
-    const output: YarnWorkspacesOutput = JSON.parse(await shell(['yarn', 'workspaces', '--silent', 'info'], {
+    const outputDataString: string = JSON.parse(await shell(['yarn', 'workspaces', '--json', 'info'], {
       captureStderr: false,
       cwd: root,
       show: 'error',
-    }));
+    })).data;
+    const output: YarnWorkspacesOutput = JSON.parse(outputDataString);
 
     const ret: Record<string, string> = {};
     for (const [k, v] of Object.entries(output)) {
@@ -96,7 +97,7 @@ async function findYarnPackages(root: string): Promise<Record<string, string>> {
  * Find the root directory of the repo from the current directory
  */
 export async function autoFindRoot() {
-  const found = await findUp('release.json');
+  const found = findUp('release.json');
   if (!found) {
     throw new Error(`Could not determine repository root: 'release.json' not found from ${process.cwd()}`);
   }
diff --git a/packages/@aws-cdk-testing/cli-integ/lib/with-cdk-app.ts b/packages/@aws-cdk-testing/cli-integ/lib/with-cdk-app.ts
index 16226c4cde259..f2b5263df06a5 100644
--- a/packages/@aws-cdk-testing/cli-integ/lib/with-cdk-app.ts
+++ b/packages/@aws-cdk-testing/cli-integ/lib/with-cdk-app.ts
@@ -4,6 +4,7 @@ import * as os from 'os';
 import * as path from 'path';
 import { outputFromStack, AwsClients } from './aws';
 import { TestContext } from './integ-test';
+import { findYarnPackages } from './package-sources/repo-source';
 import { IPackageSource } from './package-sources/source';
 import { packageSourceInSubprocess } from './package-sources/subprocess';
 import { RESOURCES_DIR } from './resources';
@@ -612,6 +613,17 @@ function defined<A>(x: A): x is NonNullable<A> {
  * for Node's dependency lookup mechanism).
  */
 export async function installNpmPackages(fixture: TestFixture, packages: Record<string, string>) {
+  if (process.env.REPO_ROOT) {
+    const monoRepo = await findYarnPackages(process.env.REPO_ROOT);
+
+    // Replace the install target with the physical location of this package
+    for (const key of Object.keys(packages)) {
+      if (key in monoRepo) {
+        packages[key] = monoRepo[key];
+      }
+    }
+  }
+
   fs.writeFileSync(path.join(fixture.integTestDir, 'package.json'), JSON.stringify({
     name: 'cdk-integ-tests',
     private: true,