Alexander Michael Karev, born Alexander Michael Evans, is an attending pediatric surgeon working at Lebackes Pediatric Surgery Clinic, with surgical priviliges at Grey Sloan Memorial Hospital. Alex is an eager and competitive surgeon, but he can also be self-absorbed and overconfident. In the early years of his internship he only wanted to work on cases that he felt were interesting. His offensive behavior and poor attitude caused him to be extremely disliked by doctors and patients alike; this changed after he started working in pediatrics. However, it is slowly revealed that Alex does care for others and is very kind. He actively plays down his soft side, adopting a brash and cocky attitude to project to other people. Alex married Izzie Stevens, but eventually divorced after she abandoned him.

Despite the callous image he projects, Alex is particularly affected when he treats addicts and abused children because of his childhood background. He initially refused to install a central line for a Demerol addict because he did not want to feed his habit. He was also able to connect with a teenage boy whose abusive father hit his mother.