The player can choose from four different Mario characters: Mario, Luigi, Princess Peach, and Yoshi.[2] The player drives a car around a party board,[3] similar to those seen in the previous Mario Party games. Depending on the character chosen, the player will start at a different area on the board.[2] The player starts with four Mushrooms.[2] Additional Mushrooms are earned by winning minigames that are played every three turns.[4] The game is over when there are no Mushrooms left. The multiplayer Party Mode that was present in all of the previous Mario Party games is no longer available, and it has been replaced by a new mode called "Shroom City". The aim of the game is to collect all the minigames and "Gaddgets" that were scattered around Shroom City by Bowser, by completing quests assigned to the player by the various inhabitants of Shroom City.
Gaddgets, invented by Professor E. Gadd, are interactive items such as a Morse code generator and a love meter.[4] The game includes over 120 minigames, including Gaddgets. Approximately 12 of the minigames can be played in multiplayer mode, with the use of a Game Link Cable. Certain Gaddgets can also be played in multiplayer mode if players control different buttons on a single Game Boy Advance system.[4] The game also included a paper game board for multiple players that could be played in conjunction with the game cartridge, used by players to roll the dice and to play minigames.[4][5]