The former Charlie's Angels star will play a love interest for Ducky (David McCallum), according to Entertainment Weekly.
Ladd played Kris Munroe on the original Charlie's Angels from 1977 to 1981. Her more recent credits include a series regular role on NBC's Las Vegas from 2003 to 2008 and guest stints on CSI: Miami and Charmed.
Last month, the producer of ABC's new Charlie's Angels reboot hinted that Ladd could make a cameo in the series.
Scott Wolf, Lily Tomlin and Jamie Lee Curtis are among the other stars due to appear in the new season of NCIS.
NCIS returns on Tuesday, September 20 at 8/7c. Ladd's episode will air in late October.
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Watch a promo for the new season of NCIS below: