The following are known Action Replay Codes for Donkey Kong Country 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
b9061533
a0f44341
d18b2a92
33d7c96f

Have Complete Scrapbook
b0c97063
2b55dbf9
26834b64
4f498ed5

Invincibility
6d957522
fa7f51e4

Infinite Lives
aa3cf642
999874d5