David Giuntoli - Julian Cadell Gibbs, Special Agent Gibbs' only son and Naval Special Warfare Operator.
Sarah Lancaster - Kathleen Gibbs, Julian's wife, and Civilian Nurse.
Mike Vogel - Joshua Patterson, Army Special Forces Captain and close friend of the Gibbs family.
Hilarie Burton - Sharon Patterson, DEA Agent, Joshua's younger sister, and friend of the Gibbs Family.
Taylor Kinney - David Reese, Jace's platoonmate and best friend.
John Krasinski - Andrew Wesson, Jace's SEAL Team 4 platoonmate and friend.
Scott Porter - Xavier Holloway, Jace's immediate superior at SEAL Team 4 and close friend.
Cobie Smulders - Lydia Brooke, Jace's close friend and Navy EOD Operator.
Richard T. Jones - Chief Warrant Officer Henry Mitchell, a Special Forces soldier.
Mike Colter - Senior Chief Drake Hall, Jace's Gold Squadron Team Leader.
Bridget Regan - CPO (later promoted to SCPO) Malia Rider US Navy CT assigned to JSOC and Jace's friend.
Lauren Cohan - CIA Officer Dylan Grey.
Gina Carano - Special Agent Raya Amato, Marine-turned-federal agent, and friend of Jace.
Demetrius Grosse - Chief Special Warfare Operator Brett Rhodes, Jace's right-hand man in November Team.