The following are known Action Replay Codes for American Idol on Nintendo Game Boy Advance (GBA).
These codes were also known as GameShark Codes and in most cases will work on both devices.

These codes are for the U.S. version of the game.

Master Code – Must Be On
71e4964a
9839fd8c
5930dbfd
69b734ca

Costumes Unlocked
f1846216
91e374ac
9b837433
c09560fa