The following are known Game Genie Codes for Ninja Gaiden on SEGA Game Gear.

• Infinite Energy
  C90 CBE 2A2
• Infinite Lives
  009 439 F79
• Start With 1 Life
  011 EDF E66
• Start With 5 Lives
  051 EDF E66
• Start With 8 Lives
  081 EDF E66
• Start On Act 2 (Smuggling)
  021 6CF E6E
• Start On Act 3 (Skyscraper)
  031 6CF E6E
• Start On Act 4 – Part 1 (Counterattack)
  041 6CF E6E
• Start On Act 4 – Part 2 (Counterattack)
  051 6CF E6E
• See End Credits
  061 6CF E6E
• Infinite Time
  C35-F6F-E61
• Start Timer At 399
  834-D7F-E60
• Start Timer At 599
  854-D7F-E60
• Almost Invincible
  000-C7E-B30
• Kill Most Level Bosses With 1 Hit
  3E2-07C-082
  012-08C-C46
  002-09C-A21
• Slow Motion!
  665-64F-E64