The family inside Firehouse 51 knows no other way than to lay it all on the line for each other. Capt. Matthew Casey (Jesse Spencer) leads the Truck Company and brash Lt. Kelly Severide (Taylor Kinney) runs the Rescue Squad.

The firehouse also includes Battalion Chief Wallace Boden (Eamonn Walker), a fireman's fireman. As chief of 51, Boden keeps his house running smoothly and his firefighters prepared to overcome all adversity. Paramedic Sylvie Brett (Kara Killmer) returns alongside seasoned veterans Christopher Herrmann (David Eigenberg) and Randy "Mouch" McHolland (Christian Stolte), as well as resourceful firefighter Stella Kidd (Miranda Rae Mayo).

Completing the team is dependable squad member Joe Cruz (Joe Minoso), daredevil Blake Gallo (Alberto Rosende), engine newbie Darren Ritter (Daniel Kyri) and the newest addition, paramedic Gianna Mackey (Adriyan Rae)