VS Gray Mann

Mann vs. Machine (commonly abbreviated as MvM) is a co-op game mode released in the Mann vs. Machine Update. In this game mode, a team of up to six players attempts to prevent a horde of AI-controlled robots from escorting a bomb to a drop-point located in a Mann Co. facility. During the game, players can purchase upgrades for their weapons and various abilities for themselves, such as various damage resistances, movement speed modifications, and improved health regeneration, using currency obtained by killing the robots, called credits. All purchased upgrades last for the duration of the game, or until the player resets their abilities at an Upgrade Station. If a player leaves the game for any reason, their upgrades are retained, providing they reconnect, as well as any credits the player has spent and/or has remaining.

Players have the option of playing Boot Camp or Mann Up. Although they do not differ in difficulty, Mann Up allows for players to receive rewards at the successful completion of a Mann Up mission and even greater rewards at the successful completion of a Tour of Duty, most notably Botkiller weapons, Australium weapons, and the exceedingly rare Golden Frying Pan. In order to play a Mann Up mission, the player must have a Tour of Duty Ticket in their backpack. Upon the completion of a Mann Up mission, the Tour of Duty Ticket used is consumed and no longer available in the player's inventory. Players can also increase the amount of item drops for their entire team in Mann Up with a Squad Surplus Voucher.

Mann vs. Machine mode currently has five separate difficulty levels: Normal, Intermediate, Advanced, Expert, and Nightmare.