Mobile Suit Gundam Seed: Battle Assault pits eight (plus four unlockable) Alliance and ZAFT pilots against each other in armored combat in the Bloody Valentine War. Each Gundam's attacks are split between physical close range attacks and long range beam/gun attacks. Gundams can boost to quickly move on the ground or change directions in mid-air, as well as enter Berserk mode that trades reduced armor for increased attack power as well as unlocking their Ultimate Attack. Before the game starts the player can reduce their boosting ability to increase their Gundam's armor or HP.
Game modes include a simple story mode, training, time attack, survival, free battle, and 2-player versus.