Steve McGarrett is a cross-over character from Hawaii Five O, where he is a Lt. Commander and a Naval Reservist who is also in charge of the Hawaii Five-0 Task Force.
Steve is also friends with NCIS Special Agent Sam Hanna with the story being that Steve owns Sam a steak dinner for some reason. Kensi Blye is the only agent from the NCIS: Office of Special Projects team to have met McGarrett in person which was shown in the first ever Hawaii Five-0 Season 2/NCIS: Los Angeles Season 3 crossover episode, Episode:Ka Hakaka Maika’i (Hawaii Five-0).
In a later episode of Season 2 of Hawaii Five-0, Steve leaves the team to go looking for his former C.O, Joe White, having believed that Joe is lying to him about "Shelburne" as Steve believes he needs to get to the bottom of why his parents were murdered and as a result of Steve's departure, his partner, Detective Danny Williams takes control of the team. (In real life, Steve leaving to go to Japan was written in due to the fact that Alex O'Loughlin, the actor who plays Steve went to rehab to seek treatment for prescription pain medication due to a recent shoulder injury).
Despite his absence, Steve is mentioned in Episode:Pa Make Loa (Hawaii Five-0) during a conversation between Sam and Detective Chin Ho Kelly. and Kensi asked about him on his search for Shelburne to Chin and Danny in Touch of Death since she came to help Steve and Joe uncover the name Shelburne.
- Despite Steve McGarrett being American, the actor who plays him, Alex O'Loughlin is originally from Australia.