One of the most effective ways to catch Moltres is to have a Pokémon with False Swipe, which can get Moltres down to 1 HP without knocking it out. You should also have a Pokémon that can paralyze or put Moltres to sleep. This will make it much easier to catch. You will need a Pokémon with Strength or Rock Smash. You will receive Rock Smash on One Island.

You will need to navigate the maze of boulders inside and out of Mt. ember in order to reach the summit.

Once Moltres’ HP has been depleted, use a Sleep or Paralyze move to bind Moltres. This will make it much easier to catch. Switch back to your Flash Fire Pokémon if you brought one with you.