Steve Carell as David Sheff

Timothée Chalamet as Nic Sheff

Maura Tierney as Karen Barbour

Amy Ryan as Vicki Sheff

Christian Convery as Jasper Sheff

Oakley Bull as Daisy Sheff

Kaitlyn Dever as Lauren

Stefanie Scott as Julia

Julian Works as Gack

Jack Dylan Grazer as 12-Year-Old Nic Sheff

Zachary Rifkin as 8-Year-Old Nic Sheff

Kue Lawrence as 5-Year-Old Nic Sheff

Timothy Hutton as Dr. Brown

Amy Forsyth as Diane

Andre Royo as Spencer

Ricky Low as Destiny

LisaGay Hamilton as Rose

Carlton Wilborn as Vince

Amy Aquino as Annie Goldblum

Marypat Farrell as Julia's Mother

Brandon James Cienfuegos as Kid

Cheska Corona as Kid

Mandeiya Flory as Kid

Martha T. Newman as Flight Attendant

Minerva García as Nurse @ Bellevue

Nikki Snipper as Airline Attendant

Anastasia Leddick as Speaker @ 12 Step Meeting

Edward Fletcher as Minister

Justin Townes Earle as Wedding Guest

Seann Gallagher as Father @ Graduation

Brooklin Thacher as Principal @ Graduation

Sasha Kelly Jackson as EMT

Tom Beyer as Meeting Leader

David Mendenhall as Rocker (uncredited)