The following are known Game Genie Codes for Phantasy Star III: Generations of Doom on SEGA Genesis.

• ETBA-AA88
  Master Code – Must Be Entered
• AWAA-CA7A
  1st treasure chest contains specified amount plus 32,768 meseta
• 9MTA-CCGN
  Start with 250 HP
• A4ZT-AA22
  Buy anything at the armor, weapon, and equipment shops no matter how much meseta you have
• ALZT-AA7W
  Items that you can afford are free
• BXDA-AA5L
  Fortune telling is free
• BXAT-AA64
  Poison recovery at the healer is free
• BW9T-AA5E
  Resurrection at the the healer is free
• A49A-AA28
  Technique distribution is free
• REHT-C6VL
  Using a Monomate, Dimate, or Trimate restores all lost HP
• BTHA-CA9J
  No TP lost for using the Res technique
• BTHA-CA38
  No TP lost for using the Rever tech.
• BTHA-CA6W
  No TP lost for using the Gires tech.
• GCJT-B62W
  No TP lost for using the Anti tech.
• CKBA-AA3G
  One strike kills small front row enemies
• B3FA-AA80
  One strike kills all large back row enemies
• GTBT-CA3T
  No HP lost in battle from enemy strikes
• GTCT-CA5C
  No HP lost in battle from enemy techniques
• ATJT-CA50
  Characters cannot be poisoned
• A2NT-AA8R
  No enemies ever attack (This code must be turned off to complete the game)