The following are known Game Genie Codes for Contra: The Alien Wars on Nintendo Game Boy.

• 017-97B-E6A
  Start with the Flame Thrower
• 077-97B-E6A
  Start with the Crush Gun
• 087-97B-E6A
  Start with the Homing Shot
• 097-97B-E6A
  Start with the Spread Shot
• 052-B1B-E6E
  Get 5 Smart Bombs after you die
• 092-B1B-E6E
  Get 9 Smart Bombs after you die
• 007-E2C-19E
  Infinite Smart Bombs
• 010-6FB-7FB
  Do not flash after getting hit
• FF0-6FB-7FB
  Flash longer after getting hit
• 3EB-81B-4CA
  You are invincible