diff --git a/icu4c/source/test/intltest/localematchertest.cpp b/icu4c/source/test/intltest/localematchertest.cpp
index 2996f8aa706d..639b58682209 100644
--- a/icu4c/source/test/intltest/localematchertest.cpp
+++ b/icu4c/source/test/intltest/localematchertest.cpp
@@ -457,7 +457,7 @@ void LocaleMatcherTest::testResolvedLocale() {
 
 namespace {
 
-bool toInvariant(const UnicodeString &s, CharString &inv, ErrorCode &errorCode) {
+bool toInvariant(const UnicodeString &s, CharString &inv, IcuTestErrorCode &errorCode) {
     if (errorCode.isSuccess()) {
         inv.clear().appendInvariantChars(s, errorCode);
         return errorCode.isSuccess();
@@ -477,7 +477,7 @@ bool getSuffixAfterPrefix(const UnicodeString &s, int32_t limit,
 
 bool getInvariantSuffixAfterPrefix(const UnicodeString &s, int32_t limit,
                                    const UnicodeString &prefix, CharString &suffix,
-                                   ErrorCode &errorCode) {
+                                   IcuTestErrorCode &errorCode) {
     UnicodeString u_suffix;
     return getSuffixAfterPrefix(s, limit, prefix, u_suffix) &&
         toInvariant(u_suffix, suffix, errorCode);
diff --git a/icu4c/source/test/intltest/numfmtst.cpp b/icu4c/source/test/intltest/numfmtst.cpp
index 3244077d796e..c855e3e29277 100644
--- a/icu4c/source/test/intltest/numfmtst.cpp
+++ b/icu4c/source/test/intltest/numfmtst.cpp
@@ -3766,7 +3766,7 @@ void NumberFormatTest::TestMismatchedCurrencyFormatFail() {
     df->setLenient(false);
     {
         Formattable result;
-        ErrorCode failStatus;
+        UErrorCode failStatus = U_ZERO_ERROR;
         df->parse(u"1.23\u20AC", result, failStatus);
         assertEquals("Should fail to parse", U_INVALID_FORMAT_ERROR, failStatus);
     }
diff --git a/icu4c/source/tools/ctestfw/tstdtmod.cpp b/icu4c/source/tools/ctestfw/tstdtmod.cpp
index 649065164b47..5a8e1ef73659 100644
--- a/icu4c/source/tools/ctestfw/tstdtmod.cpp
+++ b/icu4c/source/tools/ctestfw/tstdtmod.cpp
@@ -25,6 +25,22 @@ IcuTestErrorCode::~IcuTestErrorCode() {
     }
 }
 
+UErrorCode IcuTestErrorCode::reset() {
+    UErrorCode code = errorCode;
+    errorCode = U_ZERO_ERROR;
+    return code;
+}
+
+void IcuTestErrorCode::assertSuccess() const {
+    if(isFailure()) {
+        handleFailure();
+    }
+}
+
+const char* IcuTestErrorCode::errorName() const {
+    return u_errorName(errorCode);
+}
+
 UBool IcuTestErrorCode::errIfFailureAndReset() {
     if(isFailure()) {
         errlog(false, u"expected success", nullptr);
@@ -103,10 +119,11 @@ UBool IcuTestErrorCode::expectErrorAndReset(UErrorCode expectedError, const char
 }
 
 void IcuTestErrorCode::setScope(const char* message) {
-    scopeMessage.remove().append({ message, -1, US_INV });
+    UnicodeString us(message, -1, US_INV);
+    scopeMessage = us;
 }
 
-void IcuTestErrorCode::setScope(const UnicodeString& message) {
+void IcuTestErrorCode::setScope(std::u16string_view message) {
     scopeMessage = message;
 }
 
@@ -114,12 +131,12 @@ void IcuTestErrorCode::handleFailure() const {
     errlog(false, u"(handleFailure)", nullptr);
 }
 
-void IcuTestErrorCode::errlog(UBool dataErr, const UnicodeString& mainMessage, const char* extraMessage) const {
+void IcuTestErrorCode::errlog(UBool dataErr, std::u16string_view mainMessage, const char* extraMessage) const {
     UnicodeString msg(testName, -1, US_INV);
     msg.append(u' ').append(mainMessage);
     msg.append(u" but got error: ").append(UnicodeString(errorName(), -1, US_INV));
 
-    if (!scopeMessage.isEmpty()) {
+    if (!scopeMessage.empty()) {
         msg.append(u" scope: ").append(scopeMessage);
     }
 
diff --git a/icu4c/source/tools/ctestfw/unicode/testlog.h b/icu4c/source/tools/ctestfw/unicode/testlog.h
index 01d584c6ec81..3951e729b748 100644
--- a/icu4c/source/tools/ctestfw/unicode/testlog.h
+++ b/icu4c/source/tools/ctestfw/unicode/testlog.h
@@ -13,17 +13,11 @@
 #ifndef U_TESTFW_TESTLOG
 #define U_TESTFW_TESTLOG
 
+#include <string>
 #include <string_view>
 #include "unicode/utypes.h"
 #include "unicode/testtype.h"
 
-#if U_SHOW_CPLUSPLUS_API
-
-#include "unicode/errorcode.h"
-#include "unicode/unistr.h"
-
-#endif  // U_SHOW_CPLUSPLUS_API
-
 /** Facilitates internal logging of data driven test service 
  *  It would be interesting to develop this into a full      
  *  fledged control system as in Java.                       
@@ -31,20 +25,34 @@
 class T_CTEST_EXPORT_API TestLog {
 public:
     virtual ~TestLog();
-    virtual void errln(std::u16string_view message ) = 0;
-    virtual void logln(std::u16string_view message ) = 0;
-    virtual void dataerrln(std::u16string_view message ) = 0;
+    virtual void errln(std::u16string_view message) = 0;
+    virtual void logln(std::u16string_view message) = 0;
+    virtual void dataerrln(std::u16string_view message) = 0;
     virtual const char* getTestDataPath(UErrorCode& err) = 0;
 };
 
-#if U_SHOW_CPLUSPLUS_API
+// Note: The IcuTestErrorCode used to be a subclass of ErrorCode, but that made it not usable for
+// unit tests that work without U_SHOW_CPLUSPLUS_API.
+// So instead we *copy* the ErrorCode API.
 
-class T_CTEST_EXPORT_API IcuTestErrorCode : public ErrorCode {
+class T_CTEST_EXPORT_API IcuTestErrorCode {
 public:
     IcuTestErrorCode(TestLog &callingTestClass, const char *callingTestName)
-            : testClass(callingTestClass), testName(callingTestName), scopeMessage() {}
+            : errorCode(U_ZERO_ERROR),
+              testClass(callingTestClass), testName(callingTestName), scopeMessage() {}
     virtual ~IcuTestErrorCode();
 
+    // ErrorCode API
+    operator UErrorCode & () { return errorCode; }
+    operator UErrorCode * () { return &errorCode; }
+    UBool isSuccess() const { return U_SUCCESS(errorCode); }
+    UBool isFailure() const { return U_FAILURE(errorCode); }
+    UErrorCode get() const { return errorCode; }
+    void set(UErrorCode value) { errorCode=value; }
+    UErrorCode reset();
+    void assertSuccess() const;
+    const char* errorName() const;
+
     // Returns true if isFailure().
     UBool errIfFailureAndReset();
     UBool errIfFailureAndReset(const char *fmt, ...);
@@ -55,19 +63,18 @@ class T_CTEST_EXPORT_API IcuTestErrorCode : public ErrorCode {
 
     /** Sets an additional message string to be appended to failure output. */
     void setScope(const char* message);
-    void setScope(const UnicodeString& message);
+    void setScope(std::u16string_view message);
 
 protected:
-    virtual void handleFailure() const override;
+    virtual void handleFailure() const;
 
 private:
+    UErrorCode errorCode;
     TestLog &testClass;
     const char *const testName;
-    UnicodeString scopeMessage;
+    std::u16string scopeMessage;
 
-    void errlog(UBool dataErr, const UnicodeString& mainMessage, const char* extraMessage) const;
+    void errlog(UBool dataErr, std::u16string_view mainMessage, const char* extraMessage) const;
 };
 
-#endif  // U_SHOW_CPLUSPLUS_API
-
 #endif