Mewtwo is believed to be the strongest Pokémon in the game. That is why it is hardest to find and catch him. Here are some simple tips on how to catch Mewtwo and get one step closer to becoming a Pokémaster!
Steps

Step 1. Defeat the Elite Four
You won't be able to get Mute until you defeat the Elite Four and become a Poké Champion. You can catch Mewtwo after completing tasks on "Island 1".

Step 2. Get a National Pokédex from Professor Oak
In order for him to give it to you, you need to catch 60 Pokémon.

Step 3. Repair the "Network Machine" by finding the ruby and sapphire (see
below).
If you play Pokemon Red, Blue, Yellow, Gold, Silver, HeartGold, or SoulSilver, you can head straight to the cave in Sky City
Method 1 of 3: Getting a Ruby

Step 1. Go to "Island 1"
To do this, you need to have a Pokémon with the Surfing skill. Talk to Celio and he will explain to you that you must find an item for his car.

Step 2. Go to the entrance to the "Amber Mountain"
On the lower right side of the area, you will see some of the R Team members. You will hear the first part of the R Warehouse password. Fight them and enter the cave.

Step 3. Walk all the way to the bottom level of the cave
You don't need to read any braille charts. To get through the cave you need a Pokémon with the Strength skill.

Step 4. Take the ruby and exit the cave
Use the rope, use the "Dig" skill, or exit the same way as you entered.
Method 2 of 3: Getting Sapphire

Step 1. Go to "Island 6" and find the "Dotted Pit" that can be seen on the city map
Read the Braille sign at the entrance. It will say “Cut” on it, so be sure to capture a Pokémon with the “Cut” skill.
If you haven't rescued Lorelei from Ostorva 4 yet, the scientist will block your path

Step 2. Inside the cave, look for Braille signs
They will tell you which hole you should fall into. If there are 2 symbols on the sign, it means that you need to go up. If 5 characters - to the right. If 4 characters - left or down. If you get confused, you have to start all over again.

Step 3. On the lower level, you will see a sapphire
But don't be too happy, the super-nerd will take it first. Then he will tell you the second part of the R Warehouse password.

Step 4. Go to Warehouse R, which is located on Island 5
To get to the boss, you will have to defeat all the members of the "Team R".

Step 5. In the last room you will find a super nerd who stole the sapphire
Fight him. When you defeat him, you will receive a sapphire.

Step 6. Go to "Island 1"
Give the stones to Celio, the man who drives the machines on the island. Using a signal, he will connect the Kanto and Hohenn regions and open the passage to Mewtwo.
Method 3 of 3: Finding Mewtwo

Step 1. Go to the "Heavenly City"
In the upper left corner of the city, you will see a cave that is now open. Go north to Route 24 and use the Pokémon to Swim to the entrance.

Step 2. Inside the cave, you will need to go through the maze to reach the bottom floor
Your Pokémon must be of a high level. This area is home to very strong Pokémon (from level 46 to 70).

Step 3. At the end of the cave, you will see Mewtwo
Save the game before you engage with him, as this is your only chance to catch him, and he is very strong. See the Tips section for some tips on catching Mewtwo. You must have at least 50 ultra balls with you.
Advice
- Save before the battle and restart the game until you catch him.
- Give Mewtwo some debuffs. Freeze and Sleep are best, although others like Paralysis will do.
- If you want to keep your Master Ball, accumulate about 70 Ultra Balls. Orbs of Time will also be effective, as the chance of their success increases with the duration of the battle. They can catch Mewtwo, although it will be very difficult.
- In versions of the FireRed / LeafGreen game or newer games, a high-level Pokémon with the False Swing skill will greatly help in catching Mewtwo. False Swing is a weak attack of the Normal type that will never kill an opponent. The Parasect Pokemon is especially a good option, because it also gains the Spores skill, which, unlike the Sleep Powder skill, works 100% of the time. In HeartGold / SoulSilver games you can buy Time Balls in department stores, but in FireRed / LeafGreen you will have to bring out a male Skyeter or Nikanda with a female Paras or Parasecata on Island 4.
- Have a Tyranitar at least 56 in stock. Mewtwo's special attack, Telekinesis, has no effect on Tyranitar, giving you an advantage and the ability to deal damage with Tyranitar's Sandstorm skill. Keep throwing Ultra Balls at Mewtwo until you finally catch him.
- Capturing a high level Ditto in the cave can be very effective against Mewtwo, as this Pokemon copies all of his movements.
- The easiest way to catch Mewtwo is to use the Master Ball, which you get from the President of the Sylph Corporation in the city of Saffron. The Master Ball has a 100% success rate, regardless of the target's level and health.
- One of the strategies for capturing Mewtwo is to have a Pokémon with the Mud Bomb and Sleep Powder skills. Start putting Mewtwo to sleep, and then constantly use the Mud Bomb skill until Mewtwo is very low on health. See, don't accidentally poison him. Then start throwing Ultra Balls at Mewtwo (if Mewtwo uses the Guard skill, switch Pokémon to put him to sleep again).
- Try to fill your group with strong Pokémon over level 65. When they meet, Mewtwo will be level 70. Diversify the types of Pokémon taken, but do not take the Poisonous and Combat type Pokémon.
Warnings
-
Save.
You can only catch Mewtwo once.
- Some Pokémon in the Sky Cave (or Unknown Cave) won't let you escape, so be careful!
- It is very easy to get lost in the "Sky Cave", so if you are lost, check your position with the map.
- Maximum reflection works on Pokémon in the cave. However, if your current Pokémon is lower tier than the wild one, the reflection will not work. It is best to put the strongest Pokemon in the active slot.