Leroy Jethro Gibbs Timeline Gibbs' First Appearance JAG, Season 8, Episode 20: "Ice Queen" April 22, 2003 First NCIS Episode "Yankee White" September 23, 2003 Gibbs' Final Appearance NCIS, Season 19, Episode 4: "Great Wide Open" October 11, 2021 The NCIS: Origins episodes show Harmon's Gibbs still in Alaska after his exit from NCIS, reminiscing about his early days with the Naval Investigative Service via writing his thoughts in a journal. NCIS: Origins Cast Role Austin Stowell Leroy Jethro Gibbs Mark Harmon Older Leroy Jethro Gibbs Mariel Molino Lala Dominguez Kyle Schmid Mike Franks Tyla Abercrumbie Mary Jo Hayes Diany Rodriguez Vera Strickland