<Tr> <Td_colspan="2"> ← Previous Introductory episodes Next → Season 2 </Td> </Tr> <Tr> <Td_colspan="2"> List of NCIS episodes </Td> </Tr> <P> The first season of the American police procedural drama NCIS was originally broadcast between September 23, 2003 and May 25, 2004 on CBS . The first season dealt with introducing the characters and their strengths, skills, and weaknesses . Three recurring characters are also introduced: the main foe for the first two seasons, Ari Haswari; Special Agent Timothy McGee and Jimmy Palmer who replaces Gerald Jackson, Ducky's assistant, after he was shot . The season also introduces Sasha Alexander as Special Agent Caitlin Todd who serves as Special Agent Vivian Blackadder's (Robyn Lively) replacement, who was a member of Gibbs' team during the two - part JAG backdoor pilot . </P> <Ul> <Li> Mark Harmon as Leroy Jethro Gibbs, NCIS Senior Special Agent (SSA) assigned to Washington's Navy Yard </Li> <Li> Sasha Alexander as Caitlin Todd, former Secret Service Agent recruited to NCIS </Li> <Li> Michael Weatherly as Anthony DiNozzo, NCIS Special Agent, second in command </Li> <Li> Pauley Perrette as Abigail Sciuto, Forensic Specialist attached to NCIS </Li> <Li> David McCallum as Dr. Donald Mallard, Chief Medical Examiner for NCIS </Li> </Ul>

When did the first episode of ncis air