Ball Jacks is a competitive action game taking place in the distant future. Two robot crabs, piloted by men seeking fame and fortune, face opposite each other in an arena. Behind them is a conveyor belt with large metal balls rotating around. The goal is to capture the opponent's balls and hold them until their timer runs out. Each crab has two claws which operate independently; they can be used to grab balls from the opposite side of the screen, as well as to knock them out of the opponent's grip. The player must also be careful, as taking a hit from behind will damage the crab, and if it takes too much damage then the crab must return to the pit area to be repaired.
There are several game modes included. The main focus is the World Championship mode, in which one player takes on a succession of increasingly skilled computer opponents. Also available is a two-player versus mode with a number of handicap options. There is also a training mode where the player can freely practice to get a feel for the controls, as well as a time trial mode where the goal is to grab as many balls as possible within the time limit.