The majority of Pokémon evolve when they reach a certain level. A Pokémon "levels up" (gains a level) by gaining experience points from fights. The level that triggers an evolution varies from Pokémon to Pokémon.


If you're unsure when or how a Pokémon will evolve, this information is easy to find online. You can check the Pokémon's page on a Pokémon resource site like Bulbapedia, for instance.Note that select Pokémon will only evolve by using special items or by meeting special conditions. For example, Eevee requires an evolutionary stone to evolve no matter how many levels it gains.;
, When you get your Pokémon to a high enough level (or use an evolution stone, etc.), you will see an evolution dialogue screen with "What? (name of Pokémon) is evolving!" or a similar message. Wait for the evolution "animation" to appear. The screen may flash and the Pokémon may "blink" between its current form and its next evolution.


More modern Pokémon games generally have fancier evolution screens than older games, but the general idea is the same for all games in the series.
 As soon as you see the animation begin, press the B button rapidly. Don't wait too long or the evolution will finish.


Eventually, you will see "Huh? (name of Pokémon) stopped evolving!" or a similar message. At this point, the evolution is canceled. If your Pokémon gained a level, it will keep its level but will stay in the same form.
 Cancelling an evolution once will not cancel it in the future. If your Pokémon starts to evolve again, you will need to repeat the process above to cancel it. If you don't, it will evolve.


For Pokémon that evolve normally from leveling up, you'll need to cancel every time the Pokémon gains a level.
Wait until your Pokémon starts to evolve.
Watch for the evolution animation.
Press B repeatedly.
Repeat as needed.
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