Boo's Horror Castle is the third map in story mode in the game Mario Party 9. It is tough due to the fact that every time you pass a Boo painting a Boo will come out and move 3 spaces every time. If your the captain, and the Boo or Boo's catch you, you'll lose half your mini stars.The 2 bosses here are Dry Bones at the fort and King Boo beyond the Bowser Gate. Completing this Board allows you to move on to Blooper Beach. This board is also available at the start through party mode.
- If a Boo is going to catch you after your turn, he'll attack you first before something happens on that space.
- If two Boo catch you at once, the first Boo will take half of your Mini Stars, the second Boo will take half of your Mini Stars left after the first attack. The game only shows you the total amount of Mini Stars you lose.
- If a Boo ends up reaching the midway boss battle before the players do, he will disappear.