Most level-up evolutions happen immediately after a Pokémon gains a level once it meets the required condition. If one does not occur, check the required level, time of day, friendship value, held item, move requirement, location, form, or game version. An Everstone held by the Pokémon usually prevents evolution, and pressing the cancel button during the evolution sequence can also stop it. Some Pokémon evolve only through trading, items, or special mechanics, so leveling alone will not work. Consult a current evolution guide for your exact game and form.
