Paramedic Kimberly "Kim" Zambrano was a paramedic with the FDNY. She was portrayed by Kim Raver from the beginning of the show to the first episode of the last season.
Kim was one of two children and grew up with her single mother. Her mother married several times but also continually flew around the country in search of her husband so that Kim and her sister Melanie could grow up with a father.
She joined the FDNY as a paramedic and was partnered with Bobby Caffey, who would become her closest friend. At some stage during this time she got romantically involved with firefighter Jimmy Doherty, whom she got pregnant to and married. Kim caught Jimmy cheating on her with her sister, so the two soon got divorced and she stopped speaking to her sister.
Bobby and Kim had a very close relationship which got awkward when Bobby revealed that he was in love with her. Kim admitted she had feelings for him but didn't want to act on them because he was her best friend. The two slept together when Bobby's brother ran away, and Kim had to tell Bobby the next day it was a mistake, even though Bobby believed they were finally together.
In season 2, Bobby was fatally shot, and Kim took it incredibly rough. She attempted suicide and became depressed. She finally returned to work in season 3 and was partnered with part-time paramedic, part-time firefighter Alex Taylor. Shortly after she returned to work.
In season 4, Kim became romantically involved with writer Aaron Noble. Unbeknown to her, he was heavily involved in the drug community while working undercover for his new book, and was extremely valuable to the police, due the information he had. During this time, she had unprotected sex with him, giving her a scare that she might have been infected with a disease. Kim would suffer a terrible day at the end of season 4 when, on the same day, Taylor was killed, along with Noble and Lt. Johnson, the boss of the 55 firehouse.
Jimmy proposed to Kim but she turned him down, not knowing if he had really changed. But after she was attacked by men pretending to be police officers, Carlos be the only true love of her life. Jimmy though soon got a promotion and left, leaving Kim by herself. She soon found out she was pregnant, and hid it from the rest of the firehouse. But when it came to a risky situation at Bosco's brother's funeral, she refused to go in and help, which lead to her revealing she was pregnant with Jimmy's child.
Kim did not have much stability in her life as a child and has found as an adult, she still hasn't got any. Kim is divorced from Jimmy Doherty, and they have a son together, but never got over him and continually finds herself drawn back to him.
- Catherine Zambrano (mother)
- Melanie Zambrano (sister)
- Joey Zambrano (son)
- Jimmy Doherty (husband/ex-husband/husband)