diff --git a/icu4c/source/config/mh-mingw b/icu4c/source/config/mh-mingw
index c9999980c66..18937e0e48d 100644
--- a/icu4c/source/config/mh-mingw
+++ b/icu4c/source/config/mh-mingw
@@ -29,7 +29,8 @@ SHAREDLIBCXXFLAGS =
 SHAREDLIBCPPFLAGS = -DPIC
 
 ## Additional flags when building libraries and with threads
-THREADSCPPFLAGS = -D_REENTRANT
+THREADSCFLAGS = -mthreads
+THREADSCXXFLAGS = -mthreads
 LIBCPPFLAGS =
 
 # Commands to link. Link with C++ in case static libraries are used.
diff --git a/icu4c/source/configure b/icu4c/source/configure
index 1e58c3bb3f8..058d53a64b1 100755
--- a/icu4c/source/configure
+++ b/icu4c/source/configure
@@ -4301,6 +4301,7 @@ echo "${ECHO_T}$ac_cv_func_pthread_mutex_lock" >&6
   fi
     case "${host}" in
   *-pc-cygwin*|*-pc-mingw*)
+        ICU_USE_THREADS=1
     if test "$ac_cv_c_compiler_gnu" = no; then
             ICU_USE_THREADS=1
       if test $ENABLE_DEBUG = 1; then
diff --git a/icu4c/source/configure.in b/icu4c/source/configure.in
index 9636e98b142..9dd94e932ba 100644
--- a/icu4c/source/configure.in
+++ b/icu4c/source/configure.in
@@ -293,6 +293,8 @@ if test $threads = true; then
   dnl Check to see if we are using CygWin with MSVC
   case "${host}" in
   *-pc-cygwin*|*-pc-mingw*)
+    dnl For gcc, the thread options are set by mh-mingw/mh-cygwin
+    ICU_USE_THREADS=1
     if test "$ac_cv_prog_gcc" = no; then
       dnl We're using normal windows compilers. Threading is available.
       ICU_USE_THREADS=1