Natural Cure (Ability)/Effect

Generation III
Natural Cure heals any status conditions upon switching out.

This effect will occur if Natural Cure is the Pokémon's Ability in battle when it switches out and is not suppressed; a Pokémon that obtained the Ability with will have its status condition cured when it switches out, whereas a Pokémon which has Natural Cure but has been affected by  will not.

Generation IV onward
Natural Cure also heals any status conditions upon completing a battle (if it was in battle at the end of the battle).

Outside of battle
From Generation IV onward, Natural Cure automatically heals status conditions upon the end of a battle.