i dont think u can.

You can try to make his health the lowest possible (without killing him of course) and then burn,paralyze,freeze,poison or put him to sleep and use an ultra ball.

You paralyze him, and make him red.Throw ultra ball.by ZOLO

Make sure that mewtwo's life is red and put him to sleep and catch him with a pokeball

i got mewtwo by just by a ultruball

The only way I can think of is to save right in front of him with LOTS of ultra-balls and get lucky. That's how I got him, and all leadgendary's too.

~AquaQueen27 , the queen of pokemon blue.

how do i get a ****in mewtwo

Buy at least 90 pokeballs, then paralyze, sleep, freeze him(make sure its HP is 1, then
youcan catch it with 90 pokeballs

Catch it while in red when its asleep

Catch it while in red when its asleep

pokeballs
greatballs
ultraballs
do not use master balls.use it in entai,suicoon,or riko because they run fast.wait a
minuit this is blue version?!?!?!?!?!?!?!?!?!? oh i thought it was leafgreen
version!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!