The following are known Game Genie Codes for Mega Man III on Nintendo Game Boy.

• 02B-17F-E66
  Start with 2 lives
• 06B-17F-E66
  Start with 6 lives
• 09B-17F-E66
  Start with 9 lives
• 00C-099-3B7
  Infinite energy
• 009-77C-E6E
  Laser barriers appear and explode immediately on Spark Man Stage
• 019-53C-F76
  Takes 1 hit to kill Merciless Matt
• 0F9-53C-F76
  Takes 15 hits to kill Merciless Matt