The following are known CodeBreaker Codes for Castlevania: Circle of the Moon on Nintendo Game Boy Advance (GBA).

The codes should work with the region specified but may work for other regions as well.

• Hold R Button And Press Direction To Walk Thru Walls
  74000130 02DF
  E2000036 FFFE
  74000130 02EF
  E2000036 0001
  Note: Use the following code when using this code as well.
• Press L+R If You Get Stuck In The Ceiling
  74000130 00FF
  8200003A 00AA
• Press L For Antigravity
  D0000020 0200
  320048E0 0007
  Note: If you press L while rising up you will float until you hit a object. If you press L while dropping down you will float. If you hold L while walking off a ledge then you will walk in mid-air (Do not press while saving the game, and if you press L while on the ground you may have to get in midair and whip to become unstuck.)
• Instant Level Up
  3202566A 0001
• Max Strength
  82025646 270F
  82025648 270F
• Max Defense
  8202564E 270F
  82025650 270F
• Max Intelligence
  82025656 270F
  82025658 270F
• Max Luck
  8202565E 270F
  82025660 270F
• Infinite HP
  8202562E 270F
• Infinite MP
  82025636 270F
• Infinite Hearts
  8202563C 270F
• Max Stats
  42025646 270F
  00000004 0008
  42025648 270F
  00000004 0008
• Max Experience
  82025668 E0FF
  8202566A 5F5E
• Level Modifier
  82025664 0???
• Max Level [999]
  82025664 03E7
• Instant Level Up To Max Level
  3202566A 0020
• Have All Items
  420256EC 6363
  0000001C 0002
• Have All Magic Items
  4202572E 0101
  00000005 0002

Have Magic Items Codes

• Dash Boots
  3202572F 0001
• Double
  32025730 0001
• Tackle
  32025731 0001
• Kick Boots
  32025732 0001
• Heavy Ring
  32025733 0001
• Cleansing
  32025734 0001
• Roc Wing
  32025735 0001
• Last Key
  32025736 0001

Have Items Codes

• Leather Armor
  320256ED 0063
• Bronze Armor
  320256EE 0063
• Gold Armor
  320256EF 0063
• Chain Mail
  320256F0 0063
• Steel Armor
  320256F1 0063
• Platinum Armor
  320256F2 0063
• Diamond Armor
  320256F3 0063
• Mirrior Armor
  320256F4 0063
• Needle Armor
  320256F5 0063
• Dark Armor
  320256F6 0063
• Shinning Armor
  320256F7 0063
• Cotton Robe
  320256F8 0063
• Silk Robe
  320256F9 0063
• Rainbow Robe
  320256FA 0063
• Magic Robe
  320256FB 0063
• Sage Robe
  320256FC 0063
• Cotton Clothes
  320256FD 0063
• Prison Garb
  320256FE 0063
• Stylish Suit
  320256FF 0063
• Night Suit
  32025700 0063
• Ninja Garb
  32025701 0063
• Soldier Fatigues
  32025702 0063
• Double Grips
  32025703 0063
• Star Bracelet
  32025704 0063
• Strength Ring
  32025705 0063
• Hard Ring
  32025706 0063
• Intelligence Ring
  32025707 0063
• Luck Ring
  32025708 0063
• Cursed Ring
  32025709 0063
• Strength Armband
  3202570A 0063
• Defense Armband
  3202570B 0063
• Sage Armband
  3202570C 0063
• Gambler Armband
  3202570D 0063
• Wrist Band
  3202570E 0063
• Gaunlet
  3202570F 0063
• ArmGuard
  32025710 0063
• Magic Gaunlet
  32025711 0063
• Miracle Armband
  32025712 0063
• Toy Ring
  32025713 0063
• Bear Ring
  32025714 0063
• Potion
  32025715 0063
• Meat
  32025716 0063
• Spiced Meat
  32025717 0063
• Potion High
  32025718 0063
• Potion Ex
  32025719 0063
• Antidote
  3202571A 0063
• Cure Curse
  3202571B 0063
• Mind Restore
  3202571C 0063
• Mind High
  3202571D 0063
• Mind Ex
  3202571E 0063
• Heart
  3202571F 0063
• Heart High
  32025720 0063
• Heart Ex
  32025721 0063
• Heart Mega
  32025722 0063