- Improve all weapons
Pause the game and press Up(2), Down(2), Left, Right, Left, Right, B, A, Begin to fully upgrade all your weapons. Notice: This code can only be entered once per level, as repeating it will cause death. Also, you must have an upgradeable weapon to avoid the death effect. This code does not work on the Easy difficulty setting.

- Challenge mode bonuses
Successfully complete the indicated number of challenges to unlock the corresponding bonus:

Sheena Etranzi	28
NES Super C	8
Nobuya Nakazato interview	16
Contra 3 comic	24
Jimbo and Sully from Contra 3	The Alien Wars
Lucia character	20
NES Contra	4
Probotector character	12
Sound Test option	40

- Sound test in NES Super C
As the game's logo is fading at the Super C title screen, keep pushed Y + B and press Begin.

- Alternate colors
Successfully complete the game. At the character selection screen, press Up or Down to choose an alternate color.

- 10 lives in NES Super C
At the Super C title screen, press Right, Left, Down, Up, B, Y.

- Alternate ending
Successfully complete the game on the Normal or Hard difficulty setting to view an alternate ending.

- 30 lives in NES Contra
Before the demonstration begins at the Contra title screen, press Up(2), Down(2), Left, Right, Left, Right, Y, B, Begin.

- 99 lives
Lose a life exactly when you gain an extra life to have 99 lives. A good way to do this is by killing the mini-Boss in Level 1 because you usually get an extra life. Get hit by one of the fireballs it shoots the instant you destroy it.

- Hard mode in NES Contra
Successfully complete the game to begin a new game in Hard mode.

- Challenge mode
Successfully complete the game to unlock Challenge mode.