The following are known Action Replay Codes for Scooby-Doo! Unmasked 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
d95adbfe
93f95ad4
dad48907
c275933a

Max Health
6d25001e
4f4b525c

Infinite Health
2d6e0900
e44afea8

99 Scooby Snacks
540f6d53
ce16ebd9

Infinite Double Jumps
8088a0f2
66767cc1
8e883eff
92e9660d