A Monster House is a special type of room found in some dungeons. Monster houses will usually contain many items or Wonder Tiles. Once the player enters the room, many Pokémon in large numbers will drop down from the roof and start to gang up and attack the player. At this point, the music will change into a more menacing tone. The Pokémon inside are always ones that can be found in the dungeon it is located in. A monster house will also increase chances of a rare Pokémon to appear. Monster houses do not appear in all dungeons. Other than only appearing in certain dungeons, there are no restrictions on where a monster house can be located. They can even occur in the room the player spawns in and the room with the stairs to the next floor.
The player will realize that they are in a monster house when the music changes, Pokémon suddenly pop up all together, and the screen displays the text "It's a monster house!". If the player tries to escape, the Pokémon of the monster house will follow until they are all defeated. Another way that a player may realize that they are about to enter a monster house is when their partner Pokémon stops following them. One of the skills of all IQ groups but C, D, and G have the ability House Avoider, causing them to avoid monster houses.