the show cast consist of:
Jesse Spencer as Lieutenant Matthew Casey, the leader of Truck 81. He has a side job as a contractor.
Taylor Kinney as Lieutenant Kelly Severide, the leader of Rescue Squad 3.
Charlie Barnett as Firefighter Candidate Peter Mills, who is on Truck 81. Following in the footsteps of his father, Peter hopes to one day join the Rescue Squad. He has a sister and mother who run a family restaurant following his father's death.
Monica Raymund as Paramedic in Charge Gabriela Dawson of Ambulance 61.
Lauren German as Paramedic Leslie Elizabeth Shay of Ambulance 61. She and Kelly Severide share an apartment as roommates.
Eamonn Walker as Battalion Chief Wallace Boden as Battalion 25, a scarred veteran of the fire department. Chief Boden has unwavering dedication to the firefighters under him and has earned their loyalty and respect.
David Eigenberg as Firefighter Christopher Herrmann of Truck 81.
Teri Reeves as Doctor Hallie Thomas (Episodes 1-7), a resident at Lakeshore Hospital and Matt's former fiancée.