Worms: Ultimate Mayhem is a remastered release of Worms 4: Mayhem. A patch after the release also added in all missions from Worms 3D, making it a combined improvement of both games. The game includes five multiplayer modes (including Statue Defend, Homelands, Deathmatch etc.) for up to four players, both local and online.

Like most Worms games, the player controls a group of worms where the main objective is to use weapons such as bazookas and grenades to crush and annihilate the other worm teams. The game is turn-based, where each team may move and attack with one of their worms each turn. When hit by a enemy weapon, taking fall damage or walking on an explosive mine, the health bar decreases a little. If it reaches zero, the worm is killed in a small explosion, which can damage nearby worms. Like the 2D counterparts, the terrain is fully destructible. Elements like wind and supply drops may help or hinder in destroying the other team. Players can built custom weapons and next to graphical and AI improvements it includes a picture-in-picture display that tracks each worm that performs an action.