Q: Where is Giratina in Pokemon Platinum and how do you catch him?
A: Giratina is a single encounter legendary pokemon. He’s not extremely difficult to catch, but you only have one shot at catching him, so make sure you save your game before your attempt.
Giratina is located in the Distortion World, which you will get to in the main story line, after you beat the Galactic Hideout and make your way through Mt. Coronet. Right after you fight a boss in the Distortion World named Cyrus, you will fight Giratina, and this is your only shot to catch him, so you must come prepared.
I would suggest bringing about 40 or more ultra balls, as many revives and potions as you can bring, a pokemon with False Swipe, and preferably normal type pokemon that aren’t as vulnerable to his Ancient Power attack.
I would not suggest using a Master Ball, as there are other pokemon that are harder to catch since Giratina does not flee. Catching Giratina will just take patience and a little luck, but he’s far from impossible to catch.