By leveling it up.
Sealeo will evolve at level 50 to Walrein.
lvl 44
Sealeo evolves into Walrein at level 44 in Pokemon Pearl. Walrein can't be caught in the wild on Pokemon Pearl and must be evolved from a Sealeo.
try level 44
Level 44.
Train it to level 45.
sealeo evolves into a walrein in level 44.. good luck in your Pokemon adventure
Level 44 :D
Level 45 or its 50.
Sealeo will evolve to Walrein at level 45.
You'll need to evolve it from Sealeo at level 44.
In Pokémon Emerald, Sealeo will evolve into Walrein at Level 44.