I Know This Much Is True

Mark Ruffalo

Dominick Birdsey / Thomas Birdsey

Melissa Leo

Concettina Ipolita Tempesta 'Ma' Birdsey

Rosie O'Donnell

Lisa Sheffer

Archie Panjabi

Dr. Patel

Kathryn Hahn

Dessa Constantine

John Procaccino

Ray Birdsey

Rob Huebel

Leo

Michael Greyeyes

Ralph Drinkwater

Gabe Fazio

Shawn Tudesco / Dominick and Thomas Acting Double

Rocco Masihi

Young Thomas Birdsey

Donnie Masihi

Young Dominick Birdsey

Laura Esterman

Ruth Hood

Imogen Poots

Joy Hanks

Bruce Greenwood

Dr. Hume

Marcello Fonte

Domenico Onofrio Tempesta

Annie Fitzgerald

Miss Hanker

Joseph Ragno

Henrey Hood

Acahkos Johnson

Penny Ann Drinkwater

Jaiden Klein

Marie Sexton

Charlie Reina

Channy