Up to 32 players are supported in each multiplayer match. There are two different modes, each with six available maps: Instant Action, a deathmatch-type mode; and Power Struggle, which are played by two opposing teams, each trying to destroy the other's headquarters.
Power Struggle features the American Delta Force soldiers fighting the North Korean Army; both sides, however, have nanosuits. All players begin armed with only a pistol and a basic nanosuit, called the "prototype" suit. In order to purchase weapons and vehicles, the player must complete objectives, or kill enemies. The aim of Power Struggle is to destroy the enemy headquarters, a task which is done using either alien technology or nuclear weapons, gained by capturing alien crash sites. Without these technologies, it would be difficult to win, due to multiple automated turrets guarding headquarters; they can be destroyed only by powerful human weapons, or alien technologies. All vehicles in the game are available in Power Struggle, though they must be unlocked by capturing a zone that specializes in manufacturing a certain vehicle—for example, capturing a zone with a port would allow the building of water-based vehicles for the team in possession of the zone. However, vehicles may be stolen, by picking their locks, even if their team has not captured the zone producing that type of vehicle. Depending on the settings determined by the host, a game of Power Struggle could potentially take up to ten hours, which would cover multiple day/night cycles, if playing on a DirectX 10 server. Again, the duration of day/night cycles depends on the host's settings.
An official multiplayer map pack, the Crysis Tournament Map Pack, was released on December 24, 2007. It contains three power struggle maps and two instant action maps.