Ferdia Walsh-Peelo
as Conor "Cosmo" Lawlor

Lucy Boynton
as Raphina

Jack Reynor
as Brendan Lawlor

Ben Carolan
as Darren

Mark McKenna
as Eamon

Kelly Thornton
as Ann Lawlor

Maria Doyle Kennedy
as Penny Lawlor

Aidan Gillen
as Robert Lawlor

Ian Kenny
as Barry

Percy Chamburuka
as Ngig

Connor Hamilton
as Larry

Karl Rice
as Garry

Don Wycherley
as Brother Baxter

Des Keogh
as Brother Barnabas

Kian Murphy
as Mick Mahon

Dolores Mullally
as Dinner Lady

Marcella Plunkett
as Eamon's Mum

Vera Nwabuwe
as Ngig's Mum

Tony Doyle
as Wayne

Keith McErlean
as Barry's Dad

Art Campion
as Evan

Lydia McGuinness
as Mrs. Dunne

Kyle Bradley Donaldson
as Fifth Former

Paul Gibbons
as Exam Supervisor

Eva-Jane Gaffney
as Jacinta

Paul Roe
as Surveyor

Pádraig J. Dunne
as Surveyor