Harry Potter and the Half-Blood Prince is based on the movie of the same name. The player takes the role of Harry Potter who has to fight against Lord Voldemort and his minions.
The game allows for some freedom, as between chapters Harry can explore the school at his own pace. He can use portraits to teleport instantly to another place, or call a ghost to show him the fastest way to complete the next mission. Exploration is mainly focused on finding 150 hidden crests that unlock achievements and trophies. As Harry lost his ability to jump and climb, he must use spells to reach them.
The gameplay consists of three mini games: magic duels, brewing potions, and quidditch. In magic duels, the player learns new spells or improves existing ones by facing other magicians and using their input device to recreate a certain movement.
Quidditch is a reaction-based test where Harry's broom flies automatically, and the player can only slightly move it to fly through rings or avoid obstacles. In brewing potions, the player must recreate a recipe by using ingredients in the correct order within a time limit. They may need to heat up the bowl or stir the brew with their input device, and mistakes will result in smoke that costs time.