Kingdom Hearts was a departure from Square's standard role-playing games by introducing a substantial action-adventure element to the gameplay. In addition, it has an all-star voice cast which includes many of the Disney characters' official voice actors. Kingdom Hearts was longtime Square character designer Tetsuya Nomura's first time in a directorial position.

The game was praised for its unusual combination of action and role-playing, as well as its unexpectedly harmonious mix of Square and Disney motifs. It received numerous year-end "Best" video game awards, was a dominating presence in the 2002 holiday season, and went on to achieve Sony "Greatest Hits" status. Since its release, Kingdom Hearts has sold over 5.6 million copies worldwide and has prompted two sequels. Three more titles are currently being developed, which have a connection to a future, unannounced game.

Gameplay

File:Kingdom Hearts Battle Screenshot.png|thumb|left|The main character, Sora, fights against Heartless in the Monstro world. The head-up display consists of a game menu at the bottom left of the screen, and the character health and magic meters on the right side. Kingdom Hearts is influenced by its parent franchise, Final Fantasy, and carries gameplay elements over into its own action-based, hack and slash system. The main battle party consists of three characters: Sora, Donald Duck and Goofy. Sora is directly controlled by the player from a third person camera angle. All other party members are computer-controlled, though the player can customize their behavior to an extent through the pause menu. Donald and Goofy are the computer-controlled characters that are usable in most areas. However, nearly every world in the game features its own party member who can be chosen to replace Goofy or Donald in the party while the party is in that world. For instance, Jack Skellington can join the player's party in Halloween Town, but can not accompany the player elsewhere. On some worlds, the party changes its appearance, has abilities unique to that world, or both. For example, the party can fly in Never Land and has aquatic forms in Atlantica, which enable them to survive underwater.

Like many traditional role-playing games, Kingdom Hearts features an experience point system which determines character development. As enemies are defeated, the player gains experience which can lead up to a "level up", where the characters grow stronger and gain access to new abilities. Unlike other games of its type, Kingdom Hearts allows a certain degree of character development customization through a short tutorial found at the beginning of the game. The tutorial allows the player to select from one of three main attributes―strength, defense, and magic―for Sora to excel in and one to lack in. By choosing certain options, the player is able to manipulate how Sora learns abilities, grows statistically, and even gains levels. Donald, Goofy, and any other additional party members are assigned specific areas of strength from the outset. Donald excels in magic and Goofy excels in defense and special attacks.