The New Adventures of Mary-Kate & Ashley is a puzzle platforming game featuring Mary-Kate, Ashley, and their dog Clue. In each level, the player's goal is to flip a switch to open a cage, then grab the puzzle piece inside before the gate closes. The player can switch between the three characters at any time. Mary-Kate can jump higher, and the other two characters can jump on her head to reach high ledges. Ashley is the only one who can flip switches, and can pick up and throw Clue to move him or knock out enemies. Clue can be used as a platform, can fit through small spaces, and can swim. Enemies include monkeys, bats, and rats, and there are hazards such as spikes and crumbling platforms. If the player is having trouble reaching the puzzle piece, he or she can instead collect three clues scattered around the level, which will explain how to reach the puzzle piece.
50 levels are included, split across five cases. A password is given after every case, for resuming play at a later time.