The following are known Game Genie Codes for Alien 3 on SEGA Game Gear.

• Infinite Time (But Timer Still Counts Down)
  00B 3D6 3BE
• Infinite Energy
  002 B1C 3B7
• Infinite Lives
  00C F2A F79
• Infinite Ammo For Grenade Launcher On Pick-Up
  008 0D7 3BE
• Infinite Ammo For Flamethrower On Pick-Up
  002 6E6 19E
• Infinite Ammo For Machine Gun On Pick-Up
  006 4A7 19E
• Start With 5 Lives
  058 BA8 E66
• Start With 7 Lives
  078 BA8 E66
• Start With 9 Lives
  098 BA8 E66