Donnie Wahlberg

Detective Joel Stevens

Neal McDonough

Assistant District Attorney David McNorris

Mykelti Williamson

Police Department Detective II Bobby 'Fearless' Smith

Gary Basaraba

Police Department Police Officer III Ray Hechler

Nina Garbiras

Andrea Little, a reporter (season one)

Lana Parrilla

Teresa Ortiz, paramedic in season one, rookie police officer in season two

Jason Gedrick

Police Department Police Officer II Tom Turcotte