Sheep for the Game Boy Advance is based on the game of the same name for console and computers, but only takes the general concept, adapting it with its own graphical style, completely new levels and different playing modes.
The story revolves around a sheep dog that must herd sheep into a truck within a time limit. The player controls the dog, guiding the sheep through obstacles and dangers using various methods such as approaching them to make them move in the opposite direction or grabbing them to carry them. The dog can also bark to encourage movement and leave treats behind for the sheep to follow.
The gameplay involves more than 24 levels displayed in isometric view. Players can select from two different dogs at the start of the game, each with its own attributes such as speed and strength. Further dogs can be unlocked by playing through the game's various modes, including Normal Mode and Arrange Mode. In Normal Mode, the levels are grouped into four stages, and players can tackle them in any order within a stage before moving on to the next one. In Arrange Mode, the same stages and levels are featured, but with the added element of leveling up sheep and dog.
As players progress through the game, their dogs level up by reaching certain scores, which increase their abilities. The sheep also level up, mainly by performing certain feats within a level. However, if a sheep reaches a higher level than the dog, it becomes prone to disobedience. Once one of the regular modes is finished, a Training Mode opens up that allows players to select any level directly.