Master code:
Press Square, Circle, L2, R2 when "Press Start" appears at the title screen.

All created boxer items:
Press L1, R1, X(2), Triangle, X when "Press Start" appears at the title screen. 

Big heads:
Press Square, Circle, Up, Down when "Press Start" appears at the title screen.

Small heads:
Press Square, Circle, Down, Up when "Press Start" appears at the title screen.

Random sized boxers:
Press Square, Left, Up, Triangle when "Press Start" appears at the title screen.

Flat mode:
Press Down, Up, Circle, Square when "Press Start" appears at the title screen.

View full credits:
Press X, Triangle, Square, Circle when "Press Start" appears at the title screen.

All boxers:
Win the Bronze, Silver, and Gold belts.

Mike Tyson Challenge:
Defeat Mike Tyson and win the Gold belt to unlock the undisputed champ mode..

Fight as Mike Tyson:
Win the Gold Belt to unlock Mike Tyson in single player mode.

Fight as Iron Mike:
Win the Mike Tyson Challenge to unlock Iron Mike, the early version of Mike Tyson.


 Game Shark Codez: 
 
 Master Code (Must Be On):
 0E3C7DF2 1853E59E
 EE83A322 BCC8427A
 
 Unlock Silver Title:
 CE9AC42A BCA99B84
 
 Unlock Gold Title:
 CE9AC432 BCA99B84
 
 Unlock Tyson's Challenge:
 CE9AC4C2 BCA99B84
 
 Unlock Maskaev:
 CE9AC44A BCA99B84
 
 Unlock Grant:
 CE9AC452 BCA99B84
 
 Unlock Nicholson:
 CE9AC45A BCA99B84
 
 Unlock Johnson:
 CE9AC462 BCA99B84
 
 Unlock Byrd:
 CE9AC46A BCA99B84
 
 Unlock Tua:
 CE9AC472 BCA99B84
 
 Unlock Witherspoon:
 CE9AC47A BCA99B84
 
 Unlock Williams:
 CE9AC402 BCA99B84
 
 Unlock Holmes:
 CE9AC40A BCA99B84
 
 Unlock Rahman:
 CE9AC412 BCA99B84
 
 Unlock Tyson:
 CE9AC41A BCA99B84
 
 Unlock Iron Mike:
 CE9AC422 BCA99B84
 
 Player 1 Codez:
 
 Infinite Health:
 CE95AA58 BCA9DD4B
 CE95AA64 BCA9DD4B
 CE95AA60 BCA9DD4B
 CE95AA6C BCA9DD4B
 
 Low Health:
 CE95AA58 BCA9DB8B
 CE95AA64 BCA9DB8B
 CE95AA60 BCA9DB8B
 CE95AA6C BCA9DB8B
 
 Infinite Energy:
 CE95AA40 BCA9DD4B
 CE95AA4C BCA9DD4B
 
 No Energy:
 CE95AA40 BCA9DB83
 CE95AA4C BCA9DB83
 
 Easily TKO'd:
 0E95AA0A BCA99B83
 CE95AA0A BCA99B85
 
 Never TKO'd:
 CE95AA0A BCA99B83  
 
 Player 2 Codez:
 
 Infinite Health:
 CE95AD4C BCA9DD4B
 CE95AD48 BCA9DD4B
 CE95AD54 BCA9DD4B
 CE95AD50 BCA9DD4B
 
 Low Health:
 CE95AD4C BCA9DB8B
 CE95AD48 BCA9DB8B
 CE95AD54 BCA9DB8B
 CE95AD50 BCA9DB8B
 
 Infinite Energy:
 CE95ADB0 BCA9DD4B
 CE95ADBC BCA9DD4B
 
 No Energy:
 CE95ADB0 BCA9DB83
 CE95ADBC BCA9DB83
 
 Easily TKO'd:
 0E95AD7A BCA99B83
 CE95AD7A BCA99B85
 
 Never TKO'd:
 CE95AD7A BCA99B83