It ensnares the target in a Whirlpool, dealing 1/8 of the target's maximum HP. (1/6 if the user is holding a Binding Band) at the end of each turn for two to five turns. It also traps the target, preventing switching and escape. If a wild Pokémon uses Whirlpool on the player's Pokémon, the player may escape if the affected Pokémon has Run Away or is holding a Smoke Ball. However, these do not allow the player to switch the Pokémon out. If a trapped Pokémon uses Rapid Spin, it will be freed.
Whirlpool can hit Pokémon during the semi-invulnerable turn of Dive, and if it does, it will deal double damage. Ghost-type Pokémon cannot be trapped by Whirlpool.