Where to find Psyduck in Sun, Moon, Ultra Sun & Ultra Moon

Walk: Brooklet Hill (30%), Sandy Cave (30%, Only in Ultra Sun & Ultra Moon), Seaward Cave (30%, Only in Ultra Sun & Ultra Moon) + 2 more
SOS Encounter: Brooklet Hill, Malie Garden, Seaward Cave + 1 more
Surf: Brooklet Hill (20%), Seaward Cave (20%)
+ 1 more way

Psyduck also appears in

How to get Psyduck in Sun, Moon, Ultra Sun & Ultra Moon

Its base catch rate is 190 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 Ultra Ball.

Evolution: Psyduck → Golduck (Level 33).

Psyduck in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)