Mario Tennis Open is the first Nintendo 3DS installment of the Mario Tennis series, and the first handheld entry to be in full 3D and the first period to support online multiplayer. Most of the playable cast from Mario Power Tennis returns, but a number of others were removed and replaced by new playable characters.
The gameplay is similar to other Mario sports games, with an emphasis on quick reflexes and timing. Players can choose from a variety of power-ups and special moves to gain an advantage over their opponents.
The game features seven cups, each representing a different aspect of tennis, such as singles and doubles. The cups are competed in with either one or two players against AI opponents or other human players online. A total of 13 characters are available to play as initially but this number increases as you progress through the game.