Bowser Nightmare is the largest board in Mario Party 5, and the seventh and final board of the game. It was created from Bowser's dreams.
When players land on Happening Spaces Bowser appears and causes events that may hinder them.
- The ? Spaces at the bottom-left and bottom-right sides cause Bowser to come out for a walk to the other side. During his stroll, he turns all Blue Spaces in his path into Red Spaces and crushes any player in his path, making them lose 10 coins.
- The ? Space on the top-left and top-right sides of the board cause Bowser to appear on his Koopa Clown Car, where he forces the player to hit a red block or a blue block: one sends the player back to start while the other takes half of the player's coins.
- The ? Space at the top of the board causes Bowser to appear and take control of a flamethrower cannon. Players near the flamethrower are burned and lose their Capsules.
- The two ? Spaces near the circle at the center of the board take players into the circle (via a red Warp Pipe) where there are red and Bowser Spaces; Bowser appears for a moment to taunt the player. The two ? Spaces inside the circle take players out the circle. This is similar to the Mecha-Blooper ride from Bowser Land of Mario Party 2. If red spaces become Bowser Spaces, getting trapped in the middle results in a Bowser event every turn until the player gets out.
Story Mode
In Story Mode, Bowser and Koopa Kid are busy creating Bowser Nightmare, but when the player (Mario, Luigi, Peach, Yoshi, Wario, Daisy, or Waluigi) comes to stop them, Bowser makes Koopa Kid do the fighting for him. Koopa Kid then splits into 3 Koopa Kids: Red K. Kid, Green K. Kid, and Blue K. Kid. The player defeats all three of them and they turn back into one Koopa Kid. He escapes, but Bowser stays to challenge the player to the mini-game Frightmare. This battle takes place on a simplified version of the board. If the player defeats Bowser, the full version of Bowser Nightmare becomes playable in Party Mode.