Only in Black 2 & White 2
Hidden Grotto: Hidden Grotto
Looking for Blissey? It isn't found in the wild in this game — evolve Chansey.
Its base catch rate is 30 out of 255 (higher is easier); the catch rate calculator works out your odds with each ball. For the look, the best colour match is Love Ball or Heal Ball.
Evolution: Happiny → Chansey → Blissey.
Chansey in every game · Pokémon Black & White / Black 2 & White 2 interactive map (Unova)