diff --git a/testable-agent/src/main/java/com/alibaba/testable/agent/transformer/TestableClassTransformer.java b/testable-agent/src/main/java/com/alibaba/testable/agent/transformer/TestableClassTransformer.java
index 49b2ab8..0093e29 100644
--- a/testable-agent/src/main/java/com/alibaba/testable/agent/transformer/TestableClassTransformer.java
+++ b/testable-agent/src/main/java/com/alibaba/testable/agent/transformer/TestableClassTransformer.java
@@ -34,6 +34,7 @@ public class TestableClassTransformer implements ClassFileTransformer {
 
     private static final String FIELD_VALUE = "value";
     private static final String FIELD_TREAT_AS = "treatAs";
+    private static final String CLASS_JUNIT_5_NESTED = "Lorg/junit/jupiter/api/Nested;";
 
     /**
      * Just avoid spend time to scan those surely non-user classes, should keep these lists as tiny as possible
@@ -119,7 +120,7 @@ public class TestableClassTransformer implements ClassFileTransformer {
     }
 
     private String foundMockForTestClass(String className) {
-        ClassNode cn = ClassUtil.getClassNode(className);
+        ClassNode cn = adaptInnerClass(ClassUtil.getClassNode(className));
         if (cn != null) {
             String mockClass = lookForMockWithAnnotationAsTestClass(cn);
             if (mockClass != null) {
@@ -133,6 +134,18 @@ public class TestableClassTransformer implements ClassFileTransformer {
         return lookForOuterMockClass(className);
     }
 
+    private ClassNode adaptInnerClass(ClassNode cn) {
+        if (cn == null || cn.visibleAnnotations == null) {
+            return cn;
+        }
+        for (AnnotationNode an : cn.visibleAnnotations) {
+            if (an.desc.equals(CLASS_JUNIT_5_NESTED)) {
+                return ClassUtil.getClassNode(ClassUtil.toOuterClassName(cn.name));
+            }
+        }
+        return cn;
+    }
+
     private String lookForOuterMockClass(String className) {
         String mockClassName = ClassUtil.getMockClassName(ClassUtil.getSourceClassName(className));
         if (mockClassParser.isMockClass(ClassUtil.getClassNode(mockClassName))) {
diff --git a/testable-agent/src/main/java/com/alibaba/testable/agent/util/ClassUtil.java b/testable-agent/src/main/java/com/alibaba/testable/agent/util/ClassUtil.java
index 1b53ca2..96b140a 100644
--- a/testable-agent/src/main/java/com/alibaba/testable/agent/util/ClassUtil.java
+++ b/testable-agent/src/main/java/com/alibaba/testable/agent/util/ClassUtil.java
@@ -234,8 +234,17 @@ public class ClassUtil {
         return cn;
     }
 
+    /**
+     * Get outer class name from a inner class name
+     * @param name inner class name
+     * @return outer class name
+     */
+    public static String toOuterClassName(String name) {
+        int pos = name.lastIndexOf("$");
+        return (pos > 0) ? name.substring(0, pos) : name;
+    }
+
     private static String toDescriptor(Byte type, String objectType) {
         return "(" + (char)type.byteValue() + ")L" + objectType + ";";
     }
-
 }
diff --git a/testable-agent/src/test/java/com/alibaba/testable/agent/util/ClassUtilTest.java b/testable-agent/src/test/java/com/alibaba/testable/agent/util/ClassUtilTest.java
index 4804486..200f519 100644
--- a/testable-agent/src/test/java/com/alibaba/testable/agent/util/ClassUtilTest.java
+++ b/testable-agent/src/test/java/com/alibaba/testable/agent/util/ClassUtilTest.java
@@ -23,5 +23,13 @@ class ClassUtilTest {
             ClassUtil.fitCompanionClassName("com/alibaba/testable/demo/BlackBox$Companion"));
     }
 
+    @Test
+    void should_get_outer_class_name() {
+        assertEquals("com/alibaba/demo/basic/DemoMockTest",
+            ClassUtil.toOuterClassName("com/alibaba/demo/basic/DemoMockTest$Inner"));
+        assertEquals("com/alibaba/demo/basic/DemoMockTest",
+            ClassUtil.toOuterClassName("com/alibaba/demo/basic/DemoMockTest"));
+    }
+
 }