diff --git a/cv_bridge/CMakeLists.txt b/cv_bridge/CMakeLists.txt
index ed9f023e7..642d32fdc 100644
--- a/cv_bridge/CMakeLists.txt
+++ b/cv_bridge/CMakeLists.txt
@@ -37,13 +37,23 @@ else()
 endif()
 
 find_package(sensor_msgs REQUIRED)
-find_package(OpenCV 3 REQUIRED
+
+find_package(OpenCV 4 QUIET
   COMPONENTS
     opencv_core
     opencv_imgproc
     opencv_imgcodecs
   CONFIG
 )
+if(NOT OpenCV_FOUND)
+  find_package(OpenCV 3 REQUIRED
+    COMPONENTS
+      opencv_core
+      opencv_imgproc
+      opencv_imgcodecs
+    CONFIG
+  )
+endif()
 
 if(NOT ANDROID)
   add_subdirectory(python)
diff --git a/cv_bridge/src/CMakeLists.txt b/cv_bridge/src/CMakeLists.txt
index 39db925d7..9e2cf45e3 100644
--- a/cv_bridge/src/CMakeLists.txt
+++ b/cv_bridge/src/CMakeLists.txt
@@ -44,10 +44,14 @@ if(PYTHON_VERSION_MAJOR VERSION_EQUAL 3)
   add_definitions(-DPYTHON3)
 endif()
 
-if(OpenCV_VERSION_MAJOR VERSION_EQUAL 3)
-  add_library(${PROJECT_NAME}_boost module.cpp module_opencv3.cpp)
-else()
+if(OpenCV_VERSION_MAJOR VERSION_EQUAL 4)
+  add_definitions(-DOPENCV_VERSION_4)
+endif()
+
+if(OpenCV_VERSION_MAJOR VERSION_LESS 3)
   add_library(${PROJECT_NAME}_boost module.cpp module_opencv2.cpp)
+else()
+  add_library(${PROJECT_NAME}_boost module.cpp module_opencv3.cpp)
 endif()
 target_link_libraries(${PROJECT_NAME}_boost
   ${PYTHON_LIBRARIES}
diff --git a/cv_bridge/src/module_opencv3.cpp b/cv_bridge/src/module_opencv3.cpp
index 2aa56021f..ac93f0897 100644
--- a/cv_bridge/src/module_opencv3.cpp
+++ b/cv_bridge/src/module_opencv3.cpp
@@ -99,6 +99,11 @@ class NumpyAllocator : public MatAllocator
   NumpyAllocator() {stdAllocator = Mat::getStdAllocator();}
   ~NumpyAllocator() {}
 
+// To compile openCV3 with OpenCV4 APIs.
+#ifndef OPENCV_VERSION_4
+#define AccessFlag int
+#endif
+
   UMatData * allocate(PyObject * o, int dims, const int * sizes, int type, size_t * step) const
   {
     UMatData * u = new UMatData(this);
@@ -115,7 +120,7 @@ class NumpyAllocator : public MatAllocator
   }
 
   UMatData * allocate(
-    int dims0, const int * sizes, int type, void * data, size_t * step, int flags,
+    int dims0, const int * sizes, int type, void * data, size_t * step, AccessFlag flags,
     UMatUsageFlags usageFlags) const
   {
     if (data != 0) {
@@ -148,7 +153,7 @@ class NumpyAllocator : public MatAllocator
     return allocate(o, dims0, sizes, type, step);
   }
 
-  bool allocate(UMatData * u, int accessFlags, UMatUsageFlags usageFlags) const
+  bool allocate(UMatData * u, AccessFlag accessFlags, UMatUsageFlags usageFlags) const
   {
     return stdAllocator->allocate(u, accessFlags, usageFlags);
   }