Harvest Moon: Island of Happiness is the fourth installment of the Harvest Moon series on the DS. This version has the player take control of either two main characters, Mark or Chelsea, who are shipwrecked on an island that was once inhabited, but has since been deserted. Along with fellow survivors of the shipwreck, the player must bring life back to the island by building a farm and encouraging people from outside to move to the island.

The gameplay consists of using either the stylus pen or the d-pad and face buttons to equip tools and items. Players can raise livestock such as cows, chickens, sheep among others. A dog and a horse can be unlocked later in the game by completing certain achievements and can be used for special purposes: the dog is used to protect livestock while the horse is used for transportation and used for farm work.

Once the player gets their farm up and running more people will start to arrive to the island, setting up shops where the player can purchase more items and equipment as well as meet new friends. Players can also marry from six different bachelors or bachelorettes once the game is half-way complete, allowing new items and objectives to be unlocked.

There is also Wi-Fi capabilities where players can have their game ranked on a worldwide leaderboard as well as chat with fellow gamers through the DS' microphone.