diff --git a/dlls/msvcrt/msvcrt.spec b/dlls/msvcrt/msvcrt.spec
index ad8fa94544b..92d173118ec 100644
--- a/dlls/msvcrt/msvcrt.spec
+++ b/dlls/msvcrt/msvcrt.spec
@@ -548,6 +548,7 @@
 @ cdecl _wcsrev(wstr)
 @ cdecl _wcsset(wstr long)
 @ cdecl _wcsupr(wstr) ntdll._wcsupr
+@ cdecl _wcsupr_s(wstr long) MSVCRT__wcsupr_s
 @ cdecl _wctime(ptr) MSVCRT__wctime
 @ cdecl _wctime32(ptr) MSVCRT__wctime32
 @ cdecl _wctime64(ptr) MSVCRT__wctime64
diff --git a/dlls/msvcrt/tests/string.c b/dlls/msvcrt/tests/string.c
index fc2ad3c57ab..85447355027 100644
--- a/dlls/msvcrt/tests/string.c
+++ b/dlls/msvcrt/tests/string.c
@@ -51,6 +51,7 @@ static int (__cdecl *pstrcpy_s)(char *dst, size_t len, const char *src);
 static int (__cdecl *pstrcat_s)(char *dst, size_t len, const char *src);
 static int (__cdecl *p_mbsnbcpy_s)(unsigned char * dst, size_t size, const unsigned char * src, size_t count);
 static int (__cdecl *p_wcscpy_s)(wchar_t *wcDest, size_t size, const wchar_t *wcSrc);
+static int (__cdecl *p_wcsupr_s)(wchar_t *str, size_t size);
 static int *p__mb_cur_max;
 static unsigned char *p_mbctype;
 
@@ -597,6 +598,93 @@ static void test_wcscpy_s(void)
     ok(szDestShort[0] == 0, "szDestShort[0] not 0\n");
 }
 
+static void test__wcsupr_s(void)
+{
+    static const WCHAR mixedString[] = {'M', 'i', 'X', 'e', 'D', 'l', 'o', 'w',
+                                        'e', 'r', 'U', 'P', 'P', 'E', 'R', 0};
+    static const WCHAR expectedString[] = {'M', 'I', 'X', 'E', 'D', 'L', 'O',
+                                           'W', 'E', 'R', 'U', 'P', 'P', 'E',
+                                           'R', 0};
+    WCHAR testBuffer[2*sizeof(mixedString)/sizeof(WCHAR)];
+    int ret;
+
+    if (!p_wcsupr_s)
+    {
+        win_skip("_wcsupr_s not found\n");
+        return;
+    }
+
+    /* Test NULL input string and invalid size. */
+    errno = EBADF;
+    ret = p_wcsupr_s(NULL, 0);
+    ok(ret == EINVAL, "Expected _wcsupr_s to fail with EINVAL, got %d\n", ret);
+    ok(errno == EINVAL, "Expected errno to be EINVAL, got %d\n", errno);
+
+    /* Test NULL input string and valid size. */
+    errno = EBADF;
+    ret = p_wcsupr_s(NULL, sizeof(testBuffer)/sizeof(WCHAR));
+    ok(ret == EINVAL, "Expected _wcsupr_s to fail with EINVAL, got %d\n", ret);
+    ok(errno == EINVAL, "Expected errno to be EINVAL, got %d\n", errno);
+
+    /* Test empty string with zero size. */
+    errno = EBADF;
+    testBuffer[0] = '\0';
+    ret = p_wcsupr_s(testBuffer, 0);
+    ok(ret == EINVAL, "Expected _wcsupr_s to fail with EINVAL, got %d\n", ret);
+    ok(errno == EINVAL, "Expected errno to be EINVAL, got %d\n", errno);
+    ok(testBuffer[0] == '\0', "Expected the buffer to be unchanged\n");
+
+    /* Test empty string with size of one. */
+    testBuffer[0] = '\0';
+    ret = p_wcsupr_s(testBuffer, 1);
+    ok(ret == 0, "Expected _wcsupr_s to succeed, got %d\n", ret);
+    ok(testBuffer[0] == '\0', "Expected the buffer to be unchanged\n");
+
+    /* Test one-byte buffer with zero size. */
+    errno = EBADF;
+    testBuffer[0] = 'x';
+    ret = p_wcsupr_s(testBuffer, 0);
+    ok(ret == EINVAL, "Expected _wcsupr_s to fail with EINVAL, got %d\n", ret);
+    ok(errno == EINVAL, "Expected errno to be EINVAL, got %d\n", errno);
+    ok(testBuffer[0] == '\0', "Expected the first buffer character to be null\n");
+
+    /* Test one-byte buffer with size of one. */
+    errno = EBADF;
+    testBuffer[0] = 'x';
+    ret = p_wcsupr_s(testBuffer, 1);
+    ok(ret == EINVAL, "Expected _wcsupr_s to fail with EINVAL, got %d\n", ret);
+    ok(errno == EINVAL, "Expected errno to be EINVAL, got %d\n", errno);
+    ok(testBuffer[0] == '\0', "Expected the first buffer character to be null\n");
+
+    /* Test invalid size. */
+    wcscpy(testBuffer, mixedString);
+    errno = EBADF;
+    ret = p_wcsupr_s(testBuffer, 0);
+    ok(ret == EINVAL, "Expected _wcsupr_s to fail with EINVAL, got %d\n", ret);
+    ok(errno == EINVAL, "Expected errno to be EINVAL, got %d\n", errno);
+    ok(testBuffer[0] == '\0', "Expected the first buffer character to be null\n");
+
+    /* Test normal string uppercasing. */
+    wcscpy(testBuffer, mixedString);
+    ret = p_wcsupr_s(testBuffer, sizeof(mixedString)/sizeof(WCHAR));
+    ok(ret == 0, "Expected _wcsupr_s to succeed, got %d\n", ret);
+    ok(!wcscmp(testBuffer, expectedString), "Expected the string to be fully upper-case\n");
+
+    /* Test uppercasing with a shorter buffer size count. */
+    wcscpy(testBuffer, mixedString);
+    errno = EBADF;
+    ret = p_wcsupr_s(testBuffer, sizeof(mixedString)/sizeof(WCHAR) - 1);
+    ok(ret == EINVAL, "Expected _wcsupr_s to fail with EINVAL, got %d\n", ret);
+    ok(errno == EINVAL, "Expected errno to be EINVAL, got %d\n", errno);
+    ok(testBuffer[0] == '\0', "Expected the first buffer character to be null\n");
+
+    /* Test uppercasing with a longer buffer size count. */
+    wcscpy(testBuffer, mixedString);
+    ret = p_wcsupr_s(testBuffer, sizeof(testBuffer)/sizeof(WCHAR));
+    ok(ret == 0, "Expected _wcsupr_s to succeed, got %d\n", ret);
+    ok(!wcscmp(testBuffer, expectedString), "Expected the string to be fully upper-case\n");
+}
+
 static void test_mbcjisjms(void)
 {
     /* List of value-pairs to test. The test assumes the last pair to be {0, ..} */
@@ -721,6 +809,7 @@ START_TEST(string)
     pstrcat_s = (void *)GetProcAddress( hMsvcrt,"strcat_s" );
     p_mbsnbcpy_s = (void *)GetProcAddress( hMsvcrt,"_mbsnbcpy_s" );
     p_wcscpy_s = (void *)GetProcAddress( hMsvcrt,"wcscpy_s" );
+    p_wcsupr_s = (void *)GetProcAddress( hMsvcrt,"_wcsupr_s" );
 
     /* MSVCRT memcpy behaves like memmove for overlapping moves,
        MFC42 CString::Insert seems to rely on that behaviour */
@@ -746,5 +835,6 @@ START_TEST(string)
     test_mbcjisjms();
     test_strtok();
     test_wcscpy_s();
+    test__wcsupr_s();
     test_strtol();
 }
diff --git a/dlls/msvcrt/wcs.c b/dlls/msvcrt/wcs.c
index d83dd9458b3..0f3e9eecf25 100644
--- a/dlls/msvcrt/wcs.c
+++ b/dlls/msvcrt/wcs.c
@@ -90,6 +90,35 @@ MSVCRT_wchar_t* CDECL _wcsset( MSVCRT_wchar_t* str, MSVCRT_wchar_t c )
   return ret;
 }
 
+/******************************************************************
+ *		_wcsupr_s (MSVCRT.@)
+ *
+ */
+INT CDECL MSVCRT__wcsupr_s( MSVCRT_wchar_t* str, MSVCRT_size_t n )
+{
+  MSVCRT_wchar_t* ptr = str;
+
+  if (!str || !n)
+  {
+    if (str) *str = '\0';
+    *MSVCRT__errno() = MSVCRT_EINVAL;
+    return MSVCRT_EINVAL;
+  }
+
+  while (n--)
+  {
+    if (!*ptr) return 0;
+    *ptr = toupperW(*ptr);
+    ptr++;
+  }
+
+  /* MSDN claims that the function should return and set errno to
+   * ERANGE, which doesn't seem to be true based on the tests. */
+  *str = '\0';
+  *MSVCRT__errno() = MSVCRT_EINVAL;
+  return MSVCRT_EINVAL;
+}
+
 /*********************************************************************
  *		wcstod (MSVCRT.@)
  */