The following are known Action Replay Codes for Baseball Advance 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
727d1552
3808c931
88ac32c3
971073ba

Press Action Replay Button: Home Team Scores 100
fa692151
a2f628fd

Press Action Replay Button: Home Team Scores 0
d144da72
564b92d6

Press Action Replay Button: Away Team Scores 100
ede01e6e
9d7d014d

Press Action Replay Button: Away Team Scores 0
573380ba
c213b065

Press Action Replay Button: 3 Strikes
3684557b
78d57899

Press Action Replay Button: 0 Strikes
a5935f65
d15cf711

Press Action Replay Button: 4 Balls
f811063d
a55d3c64

Press Action Replay Button: 0 Balls
7e557033
d28404f0

Press Action Replay Button: 3 Outs
584fa1bd
03e7610e

Press Action Replay Button: 0 Outs
26d827e9
9c4cd90a