Bonanza Bros follows the story of Mobo and Robo Bonanza as they receive a mysterious task from a shadowy stranger on television. The duo must collect certain items placed in various buildings to test the security force's capabilities, with the goal of returning them successfully within three minutes. However, each building is packed with security guards who will raise an alarm if caught, and Mobo and Robo are equipped with bullets to knock the guards unconscious.
As a player, you control either Mobo or Robo, collecting treasures from ten buildings while avoiding security guards. You must navigate through the time limit and utilize an in-game map to locate the treasures. Additionally, there are bonus stages after three buildings where the objective is to collect gold bars within a limited time without being spotted by one of three spotlights. With multiple variations of these bonus stages, strategy and quick reflexes are essential to succeed.