The mode will feature an original story separate from the single-player campaign where up to four players must work together to progress and complete missions.
It was announced as part of Sony's E3 press conference, where a live demo showed three players defending their teammate who was carrying a bomb to destroy a bridge.
The game features a return to a tropical setting, with new protagonist Jason Brody hunting insane Vaas Wahine.
Ubisoft confirmed that the game will offer freedom to explore, with an entire archipelago of islands to discover in the single player campaign alone.
The limited edition Far Cry 3: Insane Edition was announced last month, including the 'Monkey Business' single-player campaign, as well as four additional single and multiplayer packs.
Far Cry 3 will be available on Xbox 360, PS3 and PC on September 4 in North America and September 7 in Europe.
> Digital Spy's E3 Gaming Expo 2012 complete coverage
Watch the Far Cry 3 gameplay trailer revealed during Ubisoft's press conference below: