Arena Trap prevents all grounded adjacent opponents from fleeing (including Teleport) or switching out as long as the user remains in battle. However, if a Pokémon with Arena Trap switches in, opponents that decided to switch out at the beginning of that turn but have not yet moved will still switch out.
If a wild Pokémon has Arena Trap and the player's Pokémon faints, if the player attempts to flee instead of sending out another Pokémon, they are unaffected by Arena Trap.
Arena Trap does not affect allies.
Ghost-type Pokémon who are normally not grounded are now immune to Arena Trap.
Outside of battle
From Pokémon Emerald onwards, if a Pokémon with Arena Trap is in the first place in the party (even if fainted), the wild Pokémon encounter rate of all Pokémon is doubled. It shares this trait with Illuminate.
In Pokémon Super Mystery Dungeon, any Pokémon adjacent to a Pokémon with the Ability Arena Trap cannot move, but are still able to use moves and items. Flying- and Ghost-type Pokémon, and Pokémon with the Ability Levitate and Run Away are unaffected.