diff --git a/icu4c/source/test/intltest/itspoof.cpp b/icu4c/source/test/intltest/itspoof.cpp
index 8980eb1f673..1e2ec174c8b 100644
--- a/icu4c/source/test/intltest/itspoof.cpp
+++ b/icu4c/source/test/intltest/itspoof.cpp
@@ -91,6 +91,7 @@ void IntlTestSpoof::runIndexedTest( int32_t index, UBool exec, const char* &name
     TESTCASE_AUTO(testBug12825);
     TESTCASE_AUTO(testBug12815);
     TESTCASE_AUTO(testBug13314_MixedNumbers);
+    TESTCASE_AUTO(testBug13328_MixedCombiningMarks);
     TESTCASE_AUTO_END;
 }
 
@@ -697,4 +698,16 @@ void IntlTestSpoof::testBug13314_MixedNumbers() {
     assertEquals("The '33' string does not fail spoof", 0, failedChecks);
 }
 
+void IntlTestSpoof::testBug13328_MixedCombiningMarks() {
+    UErrorCode status = U_ZERO_ERROR;
+    LocalUSpoofCheckerPointer sc(uspoof_open(&status));
+    TEST_ASSERT_SUCCESS(status);
+    int32_t failedChecks = uspoof_check2UnicodeString(sc.getAlias(), u"\u0061\u0F84", nullptr, &status);
+    TEST_ASSERT_SUCCESS(status);
+    assertEquals(
+            "The mismatched combining marks string fails spoof",
+            USPOOF_RESTRICTION_LEVEL,
+            failedChecks);
+}
+
 #endif /* !UCONFIG_NO_REGULAR_EXPRESSIONS && !UCONFIG_NO_NORMALIZATION && !UCONFIG_NO_FILE_IO */
diff --git a/icu4c/source/test/intltest/itspoof.h b/icu4c/source/test/intltest/itspoof.h
index e7124bd6c41..f3212a19821 100644
--- a/icu4c/source/test/intltest/itspoof.h
+++ b/icu4c/source/test/intltest/itspoof.h
@@ -52,6 +52,8 @@ public:
 
     void testBug13314_MixedNumbers();
 
+    void testBug13328_MixedCombiningMarks();
+
     // Internal function to run a single skeleton test case.
     void  checkSkeleton(const USpoofChecker *sc, uint32_t flags, 
                         const char *input, const char *expected, int32_t lineNum);
diff --git a/icu4j/main/tests/core/src/com/ibm/icu/dev/test/text/SpoofCheckerTest.java b/icu4j/main/tests/core/src/com/ibm/icu/dev/test/text/SpoofCheckerTest.java
index 44bcfb0909c..06dc008323b 100644
--- a/icu4j/main/tests/core/src/com/ibm/icu/dev/test/text/SpoofCheckerTest.java
+++ b/icu4j/main/tests/core/src/com/ibm/icu/dev/test/text/SpoofCheckerTest.java
@@ -845,4 +845,14 @@ public class SpoofCheckerTest extends TestFmwk {
         SpoofChecker sc2 = new SpoofChecker.Builder(sc1).build();
         assertEquals("Copy constructor should produce identical instances", sc1, sc2);
     }
+
+    @Test
+    public void testBug13328_MixedCombiningMarks() {
+        SpoofChecker sc = new SpoofChecker.Builder().build();
+        CheckResult checkResult = new CheckResult();
+        sc.failsChecks("\u0061\u0F84", checkResult);
+        assertEquals("The mismatched combining marks string fails spoof",
+                SpoofChecker.RESTRICTION_LEVEL,
+                checkResult.checks);
+    }
 }