No, you do not need PS Plus to play Warzone 2 on PS4 or PS5.Warzone 2.0 is truly free-to-play\n\n As stated above, the Warzone modes, as well as DMZ, are part of the game's free-to-play model, so you're good to jump into those sans subscription. It's only the multiplayer that will require PS Plus, but if you're not into that anyway, you're off the hook.
