2 species have Serene Grace as a hidden ability, 10 as a normal one

Effect, in PokéAPI's words

“Doubles the chance of moves' extra effects occurring.”

As a hidden ability

Species	Slot	Note
Deerling	Hidden
Sawsbuck	Hidden

As a normal ability

Species	Slot	Note
Chansey	Normal
Togepi	Normal
Togetic	Normal
Dunsparce	Normal
Blissey	Normal
Jirachi	Normal
Happiny	Normal
Togekiss	Normal
Meloetta	Normal
Dudunsparce	Normal

Elsewhere in PokéAPI

3 more holders without a page here

Alternate forms and other species that PokéAPI lists with Serene Grace.

Shaymin Sky, Meloetta Pirouette, Dudunsparce Three Segment