Old Ironsides is a two player game that simulates nineteenth century naval combat. The action takes place on a single screen in which each player controls a three-masted sailing vessel. The speed and movement of the ships is determined by the wind. The wind is always blowing from south to north, making southward movement difficult unless a player tacks and navigates his ship in a zigzag manner.

Each ship is equipped with twelve cannons, six on each side of the ship, and a supply of powder. The goal of the game is to defeat the opposing player in battle. A player loses if either their ship is sunk or if they get lost in the fog.