An Eeveelution is a term used for the current group of eight Pokémon that evolve from Eevee. It is a portmanteau of the words "Eevee" and "evolution". Its definition may be extended to include Eevee itself.
It is possible to get all the Eeveelutions in this game.
Vaporeon by using a Water Stone on an Eevee. Water Stones can be bought on Merson City's Market.
Jolteon by using a Thunder Stone on an Eevee. Thunder Stones can be bought on Jaeru City's Market.
Flareon by using a Fire Stone on an Eevee. Fire Stones can be bought on Botan City's Market.
Espeon by leveling up an Eevee obtained in the cave on Route 52, or by raising the first Eevee sold in Game Corner to level 20.
Umbreon by leveling up an Eevee obtained in the International Tunnel.
Leafeon by leveling up the Eevee (RINJI) obtained in a trade. The girl near Botan City wants to trade her Eevee for a Gligar.
Glaceon by raising the second Eevee sold in Game Corner to level 20.
Sylveon by using a Magic Wand on an Eevee. Magic Wand can be obtained from the scientist in the small house behind the Seneca Caverns.