The twelfth season of the police procedural drama NCIS premiered on September 23, 2014, in the same time slot as in the previous seasons, Tuesdays at 8 pm. This is the first season in which NCIS: Los Angeles did not air after NCIS. This season, NCIS: New Orleans aired after NCIS. The entire season eleven cast renewed their contracts and returned for the new season. The premiere episode aired on September 23, 2014 and was seen by 18.23 million people.
The main antagonist of the season is Sergei Mishnev, played by Alex Veadov. This character first appears in the premiere episode "Twenty Klicks".