The following are known GameShark Codes for Mary-Kate and Ashley: Winners Circle on Sony Playstation (PS1).
These codes were also known as Action Replay Codes and in most cases will work on both devices.

These codes are for the U.S. version of the game.

• Max Ribbons
  8009A870 270F
• 1 Horseshoe Needed To Have All
  D01FC9C4 0001
  801FC9C4 001A
• 1 Flag Needed To Win
  D009A42A 0001
  8009A42A 0012