Mark Ruffalo
Dominick Birdsey / Thomas Birdsey (6 eps)
Melissa Leo
Concettina Ipolita Tempesta 'Ma' Birdsey (6 eps)
Rosie O'Donnell
Lisa Sheffer (6 eps)
Archie Panjabi
Dr. Patel (6 eps)
Kathryn Hahn
Dessa Constantine (6 eps)
John Procaccino
Ray Birdsey (6 eps)
Rob Huebel
Leo (6 eps)
Michael Greyeyes
Ralph Drinkwater (6 eps)
Gabe Fazio
Shawn Tudesco / Dominick and Thomas Acting Double (6 eps)
Rocco Masihi
Young Thomas Birdsey (4 eps)
Donnie Masihi
Young Dominick Birdsey (4 eps)
Laura Esterman
Ruth Hood (3 eps)
Imogen Poots
Joy Hanks (3 eps)
Bruce Greenwood
Dr. Hume (2 eps)
Marcello Fonte
Domenico Onofrio Tempesta (2 eps)
Annie Fitzgerald
Miss Hanker (2 eps)
Joseph Ragno
Henrey Rood (2 eps)
Acahkos Johnson
Penny Ann Drinkwater (2 eps)
Jaiden Klein
Marie Sexton (2 eps)
Charles Reina
Channy (2 eps)
Violet Adams
Bunny Borsa (2 eps)
Oliver Patnode
Otero (2 eps)
Matt Helm
Young Leo (2 eps)
Derek Goh
17-19 Year Old Dominick & Thomas Acting Double (2 eps)
Agatha Nowicki
Angie Constantine (2 eps)
Irene Muscara
Prosperina Tucci (2 eps)
Adrienne R. Williams
Mrs. Birdsall (2 eps)
Tatanka Means
Nabby Drinkwater (2 eps)
Philip Ettinger
Early Adulthood Dominick Birdsey / Thomas Birdsey (2 eps)
Aisling Franciosi
Young Dessa Constantine (2 eps)
Juliette Lewis
Nedra Frank (2 eps)
Harris Yulin
Father Lavie (1 eps)
Sue Jean Kim
Dr. Yup (1 eps)
Michael Simon Hall
Stuart Feinstein (1 eps)
Gina Costigan
Mrs. O'Meara (1 eps)
Steven Cox
Boyfriend of Dr. Hume's Daughter (1 eps)
MorningStar Angeline
Nabby Drinkwater's Wife (1 eps)
Al Linea
Abruzzi (1 eps)
Richard Fitch
Mill Foreman (1 eps)
Amy Lynn Stewart
Merciful Mother (1 eps)
Guillermo Díaz
Sergeant Mercado (1 eps)
Marylouise Burke
Librarian (1 eps)
Brian Goodman
Al (1 eps)
Tim Ruddy
Robocop (1 eps)
Sandra Berrios
Social Worker at Hatch (1 eps)
Laura Silverman
Kristin (1 eps)
Christine Parks
Humanities Department Chair (1 eps)
Morgan Sullivan
Office Buddy (1 eps)
Jake Robards
Landlubbers (voice) (1 eps)
Michael Genet
Thomas' Surgeon (1 eps)
María Gonzalez
Ma's Oncology Nurse (1 eps)
A.C. Peterson
Gene Diogenes (1 eps)
Christopher J. Hanke
Thad (1 eps)
James Quattrochi
Bus Driver (1 eps)
Rachel B. Joyce
Jeanette (1 eps)
Paul Coleman
Support Group Counselor (1 eps)
Brandon J. Dirden
Kyle's Dad (1 eps)
Katt Masterson
Doreen (1 eps)
Jason Furlani
Larry Penn (1 eps)
Kate Grimes
English Professor (1 eps)
Chelsea Sheets
Brunette (1 eps)
Felix Solis
Nurse (1 eps)
Joe Grifasi
Steve Falice (1 eps)
Raymond Neil Hernandez
Omar (1 eps)
Simone Coppo
Vincenzo Tempesta (1 eps)
Sean Cullen
Dr. Yates (1 eps)
Federico Dordei
Nunzio Tucci (1 eps)
Shannon Plumb
Charlotte (1 eps)
Zaria Degenhardt
11 Year Old Concettina (1 eps)
Mark A. Gamma
Mourner Mark (1 eps)
Wayne J. Miller
Mourner Wayne (1 eps)
Thomas Gionet-Lavigne
Ray's Orderly (1 eps)
Alexander Hacker
Templeton (1 eps)
Robert Mladinich
Paddy Wagon Officer (1 eps)
Destry Allyn Spielberg
Dr. Hume's Daughter (1 eps)
Roberta Riganò
Ignazia Tempesta (1 eps)