Lego Harry Potter gameplay is much like the previous Lego games. There's more collecting, solving puzzles, and exploring. There are a lot of hidden items and secret charms to discover. Legos in this game cast spells like mages to perform attacks and combats. Potion-making is another feature, as potions can help complete the levels. Student in Peril missions are challenges to help a student, while Polyjuice Potion allows players to change another player into a mini-figure temporarily. Players can use the Leaky Cauldron to buy unlockable items and as a portal to previous levels. Hogwarts, on the other hand, offers unlockable characters by picking up lost portraits.

This is by far the cutest Lego game ever. The characters look really cute and shiny, and the environment is so colorful and interactive. The story follows the movie and the book, with much more comical twists infused in it. The AI partners usually wait for you to initiate or trigger an event in a puzzle, which is good because you won't have to depend on them to figure out how to start solving the puzzle. The camera can be a bit frustrating, as it doesnt reveal all platforms and you may die from a fall.  The multiplayer split-screen mode has no online support. In this mode, the story is a little bit tweaked to accomodate two-player interaction and coop.

Lego Harry Potter: Years 1-4 was considered by Nintendo Magazine to be one of the best Harry Potter games ever. This game received 79 out of 100, and was generally well received by critics.