The following are known Action Replay Codes for The Chronicles of Narnia: The Lion, The Witch and The Wardrobe 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
33d6580e
edd1ec3a
ccfb2864
70d3df85

Always Warm
3d3f7314
db482541

Edmund: Infinite Health
746b2612
fa2ad323

Peter: Infinite Health
c725c924
a147e9e0

Susan: Infinite Health
69a06399
9598bd7c

Lucy: Infinite Health
29e13c96
b1ee7bdf