In battle
When a Pokémon with this Ability is hit by a move that makes contact, the Pokémon with this Ability will steal the held item of the attacking Pokémon. It will not activate if the Pokémon with this Ability already has a held item. It will not activate if the Pokémon with this Ability is knocked out by that move.
If a Pokémon with this Ability is hit by a multi-strike move that makes contact (such as Fury Swipes), the item will not be stolen until after the final strike.
Pickpocket activates after Magician and the Sticky Barb, and after Thief and Covet steal a held item. Consequently, the Pokémon that has Pickpocket will always end up with the item. Pickpocket also activates after Knock Off, Bug Bite, and Pluck, meaning that the stolen item will not be lost.
The Life Orb and Shell Bell will activate before being stolen. The King's Rock and Razor Fang can still make the Pokémon with Pickpocket flinch even if stolen.
It cannot steal from a Pokémon with Sticky Hold. It cannot steal Mail. It cannot steal a Plate from a Pokémon with Multitype, a Griseous Orb if either Pokémon is Giratina, a Drive if either Pokémon is Genesect, a Red Orb if either Pokémon is Groudon, a Blue Orb if either Pokémon is Kyogre, or a Mega Stone that can Mega Evolve either Pokémon.
Outside of battle
Pickpocket has no effect outside of battle.