Dr. Alex Karev, played by Justin Chambers, is a former wrestler and studied medicine on a wrestling scholarship. Alex became a wrestler because his father, a musician,and drug addict used to beat his mother. After Alex beat his father, ending up in hospital, he left Alex and his wife behind.

Alex is a very eager intern, but he can be very overconfident and selfish. Not only that he wants to work on cases that he feels are truly interesting, but also his offensive behaviour cause him to be an outcast and extremely disliked by doctors and patients. However, Alex does also have a moral side and is the only doctor who tells the truth to patients at the risk of getting kicked out and offending patients.