M&M's Blast! is a Mario Party-style party game licensed from the candy brand. Players move their M&M candy characters (red, yellow, blue, or green) across a game board by rolling dice and deciding which way to go at a crossroads. The goal is to collect the highest number of M&M's minis. Green spaces add minis, red spaces remove them. Yellow spaces allow players to swap places with another player. Gold spaces do nothing, while blue spaces launch one of sixteen mini-games in which players compete for M&M's. These include catching falling candies, playing mini-golf, basketball or dodgeball, or a top-down race through a labyrinth to get to the sweets. Other game board spaces include teleporters and random events (wheel-of-fortune style).
Up to four players can play the game. On a single GBA, CPU players can join in, while multiplayer requires several GBAs connected via link cable. Four different game boards are available that can be played either in single games or in a tournament. A game in progress is stored to battery-backed RAM to be resumed later. The mini-games can also be played directly from the menu.