diff --git a/lib/internal/test_runner/test.js b/lib/internal/test_runner/test.js
index f2e8e41..f1d15ad 100644
--- a/lib/internal/test_runner/test.js
+++ b/lib/internal/test_runner/test.js
@@ -56,7 +56,7 @@ const {
 } = require('#internal/validators')
 const { setTimeout } = require('#timers/promises')
 const { TIMEOUT_MAX } = require('#internal/timers')
-const { cpus } = require('os')
+const { cpus, availableParallelism } = require('os')
 const { bigint: hrtime } = process.hrtime
 const kCallbackAndPromisePresent = 'callbackAndPromisePresent'
 const kCancelledByParent = 'cancelledByParent'
@@ -205,7 +205,9 @@ class Test extends AsyncResource {
 
       case 'boolean':
         if (concurrency) {
-          this.concurrency = parent === null ? MathMax(cpus().length - 1, 1) : Infinity
+          this.concurrency = parent === null
+            ? MathMax((typeof availableParallelism === 'undefined' ? cpus().length : availableParallelism()) - 1, 1)
+            : Infinity
         } else {
           this.concurrency = 1
         }