Finishes: Colors & Stains

No, you do not need to buy Call of Duty: Modern Warfare 3 to play Warzone. The latter is a standalone, free-to-play title offered by Activision.

Yes, Warzone is free in Modern Warfare 3.\n\n The cost of buying Modern Warfare 3 for multiplayer, campaign, and Zombies, however, is a different story.