Jeffrey Wright
Thelonious 'Monk' Ellison

John Ortiz
Arthur

Erika Alexander
Coraline

Leslie Uggams
Agnes Ellison

Sterling K. Brown
Clifford Ellison

Skyler Wright
Brittany

John Ales
Leo

Patrick Fischler
Mandel

Carmen Cusack
Gilda

Issa Rae
Sintara Golden

Becki Dennis
Clinic Receptionist

Tracee Ellis Ross
Lisa Ellison

Myra Lucretia Taylor
Lorraine

Kate Avallone
Woman on Patio

Dustin Tucker
Phillip

Michael Jibrin
Jelani

Michele Proude
Bulger's Nurse

David De Beck
Dr. Bulger

Okieriete Onaodowan
Van Go Jenkins

Keith David
Willy the Wonker

Miriam Shor
Paula Baderman

Raymond Anthony Thomas
Maynard

Greta Quispe
Luz Borquez

J.C. MacKenzie
Carl Brunt

Adam Brody
Wiley Valdespino

Justin Andrew Phillips
Arthur's Intern

Neal Lerner
Wilson Harnet

Jenn Harris
Ailene Hoover

Bates Wilder
Jon Daniel Sigmarsen

Michael Cyril Creighton
John Bosco

Celeste Oliva
Dr. Tiefel

Megan Robinson
Kenya Dunston

Alexander Pobutsky
Kenny

Michael Malvesti
Plainclothes Cop

Samantha Gordon
Gaby (uncredited)