Main cast •
Noah Wyle as
Dr. John Carter – Attending Emergency Physician •
Laura Innes as
Dr. Kerry Weaver – Chief of Staff •
Mekhi Phifer as
Dr. Greg Pratt – PGY-2 ER Intern •
Alex Kingston as
Dr. Elizabeth Corday – Chief of Surgery •
Goran Visnjic as
Dr. Luka Kovač – Attending Emergency Physician •
Maura Tierney as
Abby Lockhart – Fourth-year Medical Student and Nurse Manager •
Sherry Stringfield as
Dr. Susan Lewis – Attending Emergency Physician •
Ming-Na as
Dr. Jing-Mei Chen – Attending Emergency Physician •
Sharif Atkins as
Dr. Michael Gallant – PGY-1 ER Intern (episodes 1–18) •
Parminder Nagra as
Neela Rasgotra – Fourth-year Medical Student (main: episodes 3−22; recurring: episode 1) •
Linda Cardellini as
Nurse Samantha Taggart (episodes 5–22) – ER RN •
Paul McCrane as
Dr. Robert Romano – Chief of Emergency Medicine (episodes 1–8)
Supporting cast ;Doctors and medical students •
Sam Anderson as
Dr. Jack Kayson – Chief of Cardiology •
Amy Aquino as
Dr. Janet Coburn – Chief of Obstetrics and Gynecology •
John Aylward as
Dr. Donald Anspaugh – Surgeon and Hospital Board Member •
Scott Grimes as
Dr. Archie Morris – ER Second Year Resident •
L. Scott Caldwell as Dr. Megan Rabb – Director of Neo-Natology •
Glenn Howerton as Dr. Nick Cooper – ER Second Year Resident •
Bruno Campos as Dr. Eddie Dorset – Vascular Surgeon •
Maury Sterling as Dr. Nelson – Psychiatrist •
Paul Blackthorne as Dr. Jeremy Lawson – Invasive Radiologist •
Rossif Sutherland as Lester Kertzenstein – Medical Student •
Perry Anzilotti as Dr. Ed – Anesthesiologist •
Nicholas D'Agosto as Andy – Medical Student • Shi Ne Nelson as Sheila – Medical Student • K.T. Thangavelu as Dr. Subramanian • Randy Lowell as Dr. Dan Shine – Hematologist ;Nurses •
Ellen Crawford as
Nurse Lydia Wright • Conni Marie Brazelton as
Nurse Conni Oligario •
Deezer D as
Nurse Malik McGrath •
Laura Cerón as
Nurse Chuny Marquez •
Yvette Freeman as
Nurse Haleh Adams •
Lily Mariye as
Nurse Lily Jarvik •
Gedde Watanabe as
Nurse Yosh Takata •
Donal Logue as
Flight Nurse Chuck Martin •
Dinah Lenney as Nurse Shirley •
Bellina Logan as Nurse Kit •
Kyle Richards as Nurse Dori Kerns •
Liza Del Mundo as Nurse Severa •
Sumalee Montano as Nurse Duvata Mahal • Nadia Shazana as OR Nurse Jacy • Kelsey Oldershaw as Nurse Tess • Tane Kawasaki as Nurse Claire • Cynthia Cervini as Nurse Anna Waldron ;Staff, Paramedics and Officers •
Abraham Benrubi as
Desk Clerk Jerry Markovic •
Daniel Dae Kim as Social Worker Ken Sung •
Troy Evans as
Desk Clerk Frank Martin •
Kristin Minter as Desk Clerk
Miranda "Randi" Fronczak • Pamela Sinha as Desk Clerk Amira • Emily Wagner as Paramedic Doris Pickman •
Montae Russell as Paramedic Dwight Zadro • Lyn Alicia Henderson as Paramedic Pamela Olbes • Michelle Bonilla as Paramedic Christine Harms •
Demetrius Navarro as Paramedic Morales • Brian Lester as Paramedic Brian Dumar • Louie Liberti as Paramedic Bardelli • Chad McKnight as Officer Wilson •
Michael Peña as Police Officer ;Family •
Mark Valley as Richard Lockhart • Cabria Baird or Brittney Baird as Ella Greene •
Hallee Hirsh as Rachel Greene •
Michael Gross as Mr. John "Jack" Carter •
Thandie Newton as Makemba "Kem" Likasu •
George Cheung as Mr. Chen •
Kieu Chinh as Mrs. Chen •
Lisa Vidal as Sandy Lopez •
Renee Victor as Florina Lopez •
Tito Ortiz as Carlos Lopez •
José Zúñiga as Eduardo Lopez •
Paul Dooley as Harry Lewis •
Oliver Davis as Alex Taggart •
Cole Hauser as Steve Curtis •
Joy Bryant as Valerie Gallant
Special appearances •
Mary McCormack as Debbie •
Zac Efron as Bobby •
Bob Newhart as Ben Hollander •
Sarah Shahi as Tara King •
J.K. Simmons as Gus Loomer •
Jessica Chastain as Dahlia Taslitz •
Rocky Carroll as Mr. Walker •
Kevin Sussman as Colin •
Patrick Kerr as George Deakins •
Efren Ramirez as Jimmy •
Betsy Brandt as Franny Myers •
Khleo Thomas as Brian •
Richard Kline as Arnie Nadler Risk Assessment Expert •
Aisha Hinds as Medical Board Testing Administrator ==Episodes==