Of course we’ll refer to the great HomeBrew.
There is detail here: https://jjyap.wordpress.com/2014/05/24/installing-opencv-2-4-9-on-mac-osx-with-python-support/.
But if you’re in a hurry, then this post will help you.

Before this I’m sure you’ve got homebrew installed on you mac.
Go ahead.
Add homebrew/science which is where OpenCV is located using:

brew tap homebrew/science

And then, Let’s see whether opencv can be searched using:

brew info opencv

And if you’ve got problems during these two steps, try to update homebrew using:

brew update

More unfortunately, this fails again, you’ll have to take this step to force this update working.

cd /usr/local
git fetch
git reset --hard origin/master
brew update

So, back to where we break. We now can run install.

brew install opencv

And it will really take some time.

After opencv is installed, it’s not finished yet. There is a last step, make the soft link of the lib file.

cd /Library/Python/2.7/site-packages/
ln -s /usr/local/Cellar/opencv/2.4.11_1/lib/python2.7/site-packages/cv.py cv.py
/usr/local/Cellar/opencv/2.4.11_1/lib/python2.7/site-packages/cv2.so cv2.so

And of course, when you’re reading this post, the version of opencv may have been changed. So the path up there may be differet. Change it according to your opencv installed.

Done.