diff --git a/icu4c/source/extra/uconv/uconv.cpp b/icu4c/source/extra/uconv/uconv.cpp
index 581c744cfc..660cb24e37 100644
--- a/icu4c/source/extra/uconv/uconv.cpp
+++ b/icu4c/source/extra/uconv/uconv.cpp
@@ -38,10 +38,20 @@
 
 #include "unicode/uwmsg.h"
 
-#if (defined(U_WINDOWS) || defined(U_CYGWIN)) && !defined(__STRICT_ANSI__)
+#if defined(U_WINDOWS) || defined(U_CYGWIN)
 #include <io.h>
 #include <fcntl.h>
 #define USE_FILENO_BINARY_MODE 1
+/* Windows likes to rename Unix-like functions */
+#ifndef fileno
+#define fileno _fileno
+#endif
+#ifndef setmode
+#define setmode _setmode
+#endif
+#ifndef O_BINARY
+#define O_BINARY _O_BINARY
+#endif
 #endif
 
 #ifdef UCONVMSG_LINK
diff --git a/icu4c/source/tools/genrb/derb.c b/icu4c/source/tools/genrb/derb.c
index 4bf033d886..a695f4182e 100644
--- a/icu4c/source/tools/genrb/derb.c
+++ b/icu4c/source/tools/genrb/derb.c
@@ -33,6 +33,17 @@
 #if defined(U_WINDOWS) || defined(U_CYGWIN)
 #include <io.h>
 #include <fcntl.h>
+#define USE_FILENO_BINARY_MODE 1
+/* Windows likes to rename Unix-like functions */
+#ifndef fileno
+#define fileno _fileno
+#endif
+#ifndef setmode
+#define setmode _setmode
+#endif
+#ifndef O_BINARY
+#define O_BINARY _O_BINARY
+#endif
 #endif
 
 #define DERB_VERSION "1.0"
@@ -285,7 +296,7 @@ main(int argc, char* argv[]) {
             if (tostdout) {
                 out = stdout;
 #if defined(U_WINDOWS) || defined(U_CYGWIN)
-                if (_setmode(_fileno(out), _O_BINARY) == -1) {
+                if (setmode(fileno(out), O_BINARY) == -1) {
                     fprintf(stderr, "%s: couldn't set standard output to binary mode\n", pname);
                     return 4;
                 }