Mat Block protects all Pokémon on the user's side of the field from any moves except status moves for that turn. Unlike Protect, this move is not an increased priority move. Similar to Fake Out, Mat Block will only work if used on the first turn after the Pokémon enters the field; the Pokémon must be switched out and back in to be able to use Mat Block again.
It protects from physical and special moves. Its chance of failing rises if used in a row.* You and your teammates in the same room will get Mat Block status, which protects you from physical and special moves. But its chance of failure rises if you use it after you use a move that evades enemies' attacks.*
Mat Block appears at the start of Greninja's Final Smash, Secret Ninja Attack. The initial Mat Block flip sends opponents into the air, allowing Greninja to slice them repeatedly before launching them with a final blow.
This move is a reference to a trick that has been used by ninjas, which involves flipping a tatami (a type of mat used as a flooring material in traditional Japanese-style rooms) to block incoming projectile attacks.