The user switches held items with the target. If only one of them is holding an item, the item is moved to the other.
Trick fails if neither Pokémon has a held item, if the user is a wild Pokémon, if either Pokémon is holding Griseous Orb, if the target is behind a substitute, or if the target has Sticky Hold (even if it has no held item). It also fails if either Pokémon has Multitype.
In link battles, battle facilities, Secret Bases, and the Trainer House, items stolen will be returned at the end of the battle.
In Japanese Pokémon Ruby and Sapphire, Trick can exchange Mail, but causes the Trick Mail bug. In international releases of Pokémon Ruby and Sapphire, as well as all releases of subsequent games, Trick will fail if either Pokémon is holding Mail.
Generation V onwards
Trick no longer switches a Trainer's Pokémon's items permanently; however, items switched in wild battles are permanently switched.
Trick can now exchange a Griseous Orb as long as neither the user nor the target is Giratina. Trick can now exchange items with a Pokémon that has Multitype (but still cannot exchange Plates with Arceus).
If powered up by a Psychium Z into Z-Trick, the user's Speed is raised two stages, then the move itself will fail after obtaining the Z-Power since it won't be possible to exchange its own Z-Crystal.
Trick will always fail when used against the raid boss in a Max Raid Battle, regardless of item. It can be used successfully against Dynamax Pokémon in standard trainer battles, subject to the above list of exceptions.
In Generation IV, despite being able to learn this move via Move Tutor, it will always fail when used by Arceus due to its Ability Multitype. In later generations, it can successfully use the move as long as neither Pokémon is holding a Plate.