The following are known Action Replay Codes for Kirby & the Amazing Mirror 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
156e6b51
38ef9b07
ad5bac98
df7b47e1

Infinte Health
204aaa47
ab715c33

Max Health
56fa986f
63a76fcf

Invincibility
780f91e4
972fa220

Infinite Lives
3a7aad07
1c0137f1

Infinite Batttery
1a4632fb
be8a7506