Paramedic Carlos Nieto is a paramedic with the FDNY. He was portrayed by Anthony Ruivivar and remained on the show for all six seasons.
Carlos Nieto was born on May 11, 1975 in Hawaii. Born of Filipino heritage, he was originally named Adam, and had an older brother named Christian. After their parents split up, Christian stayed with their mother, while their father took Adam to New York. Their father he was the victim of a hit-and-run vehicle accident, which killed him. Young Carlos was found holding his father's hand. In the aftermath of his father's death, Carlos was placed in an orphanage run by nuns, where he grew up not knowing about his past and believing he had been abandoned by his mother at the orphanage. He went through 6 or 7 foster homes, and one of his foster mothers was named Lucinda Harding.
After leaving school, Carlos joined the Marines, serving as a medic. After his discharge, Carlos wished to go to medical school. To earn some money during his schooling, he joined the FDNY as a paramedic, where he was partnered up with Monte 'Doc' Parker. The two men did not get on at first, especially after Doc's partner Jerry left on disability pay, and they came to blows a few times. However, Carlos looked up to Doc as a father figure, and was annoyed when Doc reassigned him to be partnered him with another paramedic, Alex Taylor. Doc had done so in order that he himself could ride with paramedic Kim Zambrano following her return to work. Carlos' other friends include his roommate Ty Davis, and his pet cockatoo (named simply "Bird"), which he obtained from a dead homeless guy.
Not long after starting work, Carlos and Doc treated a girl named Vangie. She fell for Carlos and they started dating, but she turned to be mentally unstable and Carlos broke it off with her. This caused her to attempt suicide, after which she revealed she was pregnant. Carlos offered to pay for an abortion, but Vangie merely told him he "wouldn't have to worry about it anymore". Two years later, Carlos he will be good father to he'sdaughter Kylie, he will give family to her kennedy family lost custdoy
In 2003, Carlos was suspended after allegations that he had abused a teenage girl, Nicole West, in the ambulance. It had been a simple, accidental touch for which he had apologised to her straight away, but no-one at the firehouse, apart from Doc believed him. He win custody of he's daughter back and drop out of medical school. Doc put Carlos back on active duty, an action which got Doc into trouble. As part of the settlement against the West family, Carlos was dismissed. It later turned out that Nicole was really being abused by her stepfather, and was trying to reach out for help by blaming Carlos. When the truth was revealed, Carlos was reinstated in his job. After that incident was resolved, Carlos decided that being a paramedic was what he really wanted to do, and decided not to go to medical school.
A year later, Carlos found out that his daughter Kylie had a medical condition known as diopathic aplastic anemia, and that she needed a bone marrow transplant. He offered his marrow, but he was not a match. This led him to try and find his biological family to save Kylie, and allowed his brother to finally find him. Christian was a match, and told Carlos of his true origins.
After Doc slowly started going insane, which ended up with him shooting Captain Steeper, Carlos was the first to defy his friend and treat Steeper, trusting Doc would not harm him (which he didn't). When Doc ended up in Bellevue Mental Hospital, Carlos kept in contact with his former mentor. In the final episode of the series, Carlos married fellow paramedic, Holly Levine, at the end of the series.
- Unnamed Father [deceased]
- Christian (brother)
- Holly Levine Nieto (wife)
- Kylie Samstron Nieto (daughter)