How did Ducky die in NCIS? The goodbye was written by one of his own co-stars
David McCallum played Dr. Donald "Ducky" Mallard from the 2003 premiere onward and was the last original cast member left standing. He died on September 25, 2023, at 90. Five months later NCIS gave the character an ending — and handed the script to the actor who'd spent 20 years working across from him.
The short answer
Ducky dies peacefully in his sleep, off screen, between episodes. The reveal opens season 21, episode 2, "The Stories We Leave Behind," which aired February 19, 2024 on CBS. Jimmy Palmer stops by Ducky's house with coffee to drive him to work, the way he does every morning, and finds his mentor gone.
Who wrote it
Brian Dietzen — Jimmy Palmer himself, on the show since season 1 — co-wrote the episode with executive producer Scott Williams, his longtime writing partner. Dietzen had spoken at McCallum's memorial service in New York that January. He's said filming the cold open, in which his own character discovers the body, wrecked him.
The pair deliberately avoided a clip show.
The best way to honor the character, Dietzen told USA Today in 2024, was to let him "solve one last case with the team."
The last case
That case involves a woman whose father was dishonorably discharged from the Marines. Working from notes Ducky had kept to himself, the team clears the veteran's name. Ducky effectively cracks it posthumously. Archive footage from earlier seasons is threaded through the hour, but the episode functions as an actual NCIS case, which was the point.
The surprise in the last minutes
Michael Weatherly walks back in as Tony DiNozzo — his first appearance since leaving in 2016 — not to work the case, but to check on Jimmy. Dietzen told TV Insider in 2024 that Weatherly was brought in and shot under near-total secrecy, and that the character's long friendship with Palmer was the reason producers chose him over other returning options.
Why Ducky had barely been on screen
McCallum stepped back from regular appearances after season 15 but stayed credited as a series regular and dropped in periodically, last appearing in the season 20 finale in 2023. The show covered his absences by sending Ducky on a book tour — which is exactly what the character is meant to have just returned from when Jimmy lets himself in.
For the record: season 21 ran only 10 episodes because of the 2023 strikes. Two of them were milestones — Ducky's farewell, and the NCIS franchise 's 1,000th episode.