Caeley Griffin As the Mac's current configuration goes, no, HOWEVER, it is possible!
For one, you would need a native install of Windows, so dual booting Windows and MacOS, because Overwatch is made only for Windows.
Second, since Macs have Thunderbolt, you can buy and use an external video card. Well, you would have to buy the external video card case and the video card separate in most cases, but some products come with it bundled together.
Which specific Mac do you have?