For more than two decades, David McCallum was Ducky to NCIS fans.
To Mark Harmon, though, he was also an actor who impressed him before their long run together had even really begun.
When McCallum died on September 25, 2023, at the age of 90, Harmon went back to his first memory of meeting the man who would become one of his longest-running NCIS co-stars.
“David lived a great, full, long life,” Harmon said. “I was in awe when I first met him and all of us on the show were honored to have toed a mark opposite him. My condolences go out to Katherine and his family.”
Harmon shared the tribute with TVLine shortly after McCallum’s death. Read Mark Harmon’s original tribute at TVLine
It was only a few sentences, but coming from someone who had worked beside McCallum for nearly 20 years, “I was in awe” said plenty.
Harmon and McCallum Were There From the Beginning
Mark Harmon and David McCallum were both part of NCIS when the series launched in 2003.
Harmon played Special Agent Leroy Jethro Gibbs, the demanding team leader who rarely said more than he needed to. McCallum played Dr. Donald “Ducky” Mallard, the medical examiner who could turn almost any conversation into a story about something he had seen, read or experienced years earlier.
The personalities were completely different.
That was part of what made Gibbs and Ducky work so well together.
Ducky was one of the few people who had known Gibbs long enough to understand what sat underneath all those silences. Their friendship existed before most of the team came into Gibbs’ life, and the show gradually filled in pieces of that history over the years.
Off camera, Harmon clearly respected the man standing opposite him just as much.
McCallum stayed with NCIS through its first 20 seasons, although his appearances became less frequent toward the end. His final Season 20 appearances were made remotely.
On September 25, 2023, McCallum died of natural causes at NewYork-Presbyterian Hospital in New York. TVLine’s report on David McCallum’s death
He had turned 90 just days earlier.
The People Who Worked With Him Remembered More Than Ducky
Harmon wasn’t alone in remembering McCallum.
Michael Weatherly, Pauley Perrette, Brian Dietzen and other members of the NCIS family shared their own memories after his death.
Weatherly remembered a man who made the most of the time he had, while Perrette’s tribute focused heavily on something fans didn’t necessarily get to see on television: how much McCallum loved his family. Read the NCIS cast tributes at TVLine
That part of McCallum’s life came through even more strongly in the words of his son, Peter.
Peter described his father as deeply curious about the world around him. McCallum didn’t simply memorize medical language for Ducky. Over the years, he studied the subject so seriously that his family marveled at how much real knowledge he had picked up.
That sounds almost exactly like Ducky.
But McCallum had been living an unusually full life long before anyone at NCIS handed him a bow tie.
David McCallum Was Famous Long Before NCIS
For viewers who discovered him through NCIS, it can be easy to forget just how far back McCallum’s career went.
He appeared in films including A Night to Remember and The Great Escape, but his first enormous wave of fame came in the 1960s when he played secret agent Illya Kuryakin on The Man from U.N.C.L.E.
The role turned him into an international star.
Decades later, McCallum somehow found another character that would introduce him to an entirely new generation.
Ducky could have been little more than the man who explained a cause of death and sent Gibbs back out into the field.
McCallum made him much more than that.
He gave Ducky warmth, humor and endless curiosity. The character talked to the dead on his autopsy table as if they were still in the room. He could irritate Gibbs with a long story one minute and understand exactly what his old friend needed the next.
And when Jimmy Palmer came into his life, viewers got to watch Ducky become a mentor too.
That relationship would become particularly important when NCIS eventually had to say goodbye.
NCIS Gave Ducky the Goodbye David McCallum Deserved
Five months after McCallum’s death, NCIS addressed the loss directly.
Season 21’s second episode, “The Stories We Leave Behind,” aired on February 19, 2024. The story begins with Jimmy Palmer learning that Ducky has died, before the team discovers one of the cases he had left unfinished.
Instead of spending the entire hour simply talking about Ducky, they honor him by doing something he would have understood better than most: helping someone whose story still needed to be heard.
CBS described the episode as the team finding comfort in completing one of Ducky’s unfinished cases. See the official CBS episode listing
There was another reason the episode felt personal.
Brian Dietzen, who had spent years playing Ducky’s protégé Jimmy Palmer, helped write it.
And near the end came a surprise that CBS had managed to keep quiet.
Tony DiNozzo walked back into the building.
Michael Weatherly returned for the first time in years and found Jimmy preparing for Ducky’s funeral. Tony handed him a black bow tie — a small nod to the man they were both about to say goodbye to.
It wasn’t a huge reunion with every former cast member.
It didn’t need to be.
Tony showing up for Palmer made the world of the show suddenly feel connected again, and the episode ended with a memorial to McCallum himself. Read about Michael Weatherly’s return for the Ducky tribute
Mark Harmon did not appear as Gibbs in the episode.
Considering how much history Gibbs and Ducky shared, his absence naturally stood out to some viewers. The show’s producers later explained that they didn’t want to bring Gibbs back for a brief appearance simply because the occasion demanded one. Read the producers’ explanation at TVLine
But Harmon’s words about McCallum were already part of the real-life farewell.
Ducky’s Story Didn’t End There
There has been one unexpected development since that tribute episode.
NCIS has found a way to tell new Ducky stories without McCallum.
In October 2025, Adam Campbell returned as a younger Donald Mallard in the NCIS prequel NCIS: Origins.
Campbell had played young Ducky before on the original series, but Origins gave the character a much bigger role in Gibbs’ early history.
In the Season 2 episode “The Edge,” Ducky arrives at Camp Pendleton from Washington as a liaison tasked with evaluating whether the office needs its own medical examiner.
CBS described him as an “old acquaintance” of Gibbs, giving viewers another look at a friendship we already knew would last for decades. See CBS’s official listing for “The Edge”
And that wasn’t a one-off appearance.
Young Ducky returned again in March 2026, when Campbell appeared in the NCIS: Origins episode “Homeward Bound.” This time, Ducky helped the team investigate a case involving stolen human remains. See the CBS episode listing for Ducky’s 2026 return
So even after David McCallum’s death, the friendship between Gibbs and Ducky is still being explored.
That makes Harmon’s original tribute feel a little different three years later.
“I Was in Awe”
Mark Harmon had spent nearly two decades working with McCallum by the time they filmed their final years together on NCIS.
There were hundreds of episodes behind them.
Countless scenes between Gibbs and Ducky.
A television friendship that had become familiar enough that viewers didn’t need an explanation whenever Ducky called him “Jethro.”
Yet when Harmon had to put his feelings about McCallum into words, his mind went all the way back to the beginning.
“I was in awe when I first met him.”
After everything that came afterward, maybe that first impression never really changed.
