Baneful Bunker prevents any attacks targeted at the user from striking, for the duration of the turn. If a contact move is targeted at the Baneful Bunker user on that turn, the attacker becomes poisoned. It has priority +4 so will activate before most other moves.

Poison or Steel type Pokémon, those with the ability Immunity or those behind a Substitute cannot be poisoned. The effects do not stack with the Rocky Helmet item or the Rough Skin or Iron Barbs abilities.

The accuracy of Baneful Bunker drops by 1⁄3 each time it is used consecutively after itself or Protect, Detect, Endure, Wide Guard, Quick Guard, Spiky Shield, or King's Shield.

When a Pokémon is holding Poisonium Z and uses its Z-Power, Baneful Bunker turns into Z-Baneful Bunker and raises Defense one stage, in addition to its usual effect as above.