Walkthrough
After defeating the Elite Four, you will finally earn access to Cerulean Cave just outside Cerulean City. At the bottom of the Cerulean Cave is the Legendary Pokemon Mewtwo, the strongest Wild Pokemon in the entire game. In order to have the opportunity to catch Mewtwo, you must first defeat it in battle. The battle will have a five minute time limit, and Mewtwo will have all of its Stats raised as the battle begins. Unfortunately, since Mewtwo is a Psychic Type Pokemon, it is truly only weak to Dark Type Attacks, Bug Type Attacks, and Ghost Type Attacks. Even though Mewtwo isn't weak to them, Steel Types also work well against it since they don't take much damage from its Attacks.
After defeating Mewtwo in battle, you will be able to catch it like any other Wild Pokemon Encounter. However, it has more unique features to it than other Wild Pokemon. You see, Mewtwo will be able to randomly cause a barrier to appear when you're trying to capture it. When its barrier is active, it will remove the effects of all Berries currently being used on it, preventing any Poke Balls or other Berries from landing on it while the barrier is present. If you still have your Master Ball, Mewtwo is the perfect Pokemon to use it on. However, Ultra Balls and Razz Berries can also work.
Level 70 Mewtwo: Psychic, Recover, Amnesia, Swift
Need help catching Mewtwo? Check out our How To Easily Catch Mewtwo Page!