The following are known Action Replay Codes for Yu-Gi-Oh! World Championship Tournament 2004 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
b8de9a14
4b4ed4fa
c0befa41
55347213

Have All Cards
e38f97d6
846fb436

Infinite LP
d7a23a6a
87f4b5d1

Instant Win
481a736b
01134e5a