“The Tonight Show Starring Jimmy Fallon” showrunner Jim Bell is walking away from NBC after nearly three decades at the troubled network.

Bell started at NBC in 1990 as a segment producer for the Olympic Games and worked his way up to the executive producer gig at “Today,” where he oversaw the flagship morning show for seven years. Bell was named president of NBC Olympics production and programming in 2017 -- but network honchos later asked him to pivot to “The Tonight Show” last year to help the show compete with the politics-heavy “Late Show with Stephen Colbert” at rival CBS.

Bell obliged, but he’s now walking away from the Peacock Network altogether.

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“As has been the case for my nearly 30 years at NBC, I said yes to their request, adding only that I would commit for a year and we would review the situation at that time,” Bell said in a statement provided to Fox News. “After serious contemplation, I realized I did not want to extend my time at the show.”

Jim Bell started at NBC in 1990 as a segment producer for the Olympic Games (Photo by Eric Dubost/Pacific Press/LightRocket via Getty Images, File)

Bell said that his thoughts were “part of larger ones” about his career, and what emerged was “a strong desire to delve into something new” and build on “experience in news, sports, and entertainment so I can broaden and deepen my leadership role” in the media industry.

“I will always look back on my years at NBC as an extraordinary chapter in my life, and thank the many talented individuals who have joined me in truly meaningful work around the globe,” Bell said.

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Gavin Purcell, who recently signed a producing deal with NBCUniversal, is to replace Bell on an interim basis.

Bell’s loss has been considered a major blow to NBC, which has been plagued with negative headlines for roughly two years as the network came under fire for various sexual misconduct scandals.

“Jim's imprint at 'The Tonight Show' was substantial and will be long-lasting,” NBCUniversal Content Studios Vice President George Cheeks said. “With his decades of production expertise, Jim was able to elevate our live telecasts to new heights and took 'Tonight' on the road and delivered shows that raised the bar. We wish him nothing but the best moving forward and thank him for his contributions.”

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Bell, a graduate of Harvard University, had a significant impact on NBC over three decades but it wasn’t all positive. He was at the helm of “Today” when fan favorite Ann Curry was shown the door with a controversial, teary-eyed on-air goodbye. Bell also oversaw now-disgraced anchor Matt Lauer when much of his alleged sexual misconduct occurred.

NBCUniversal has refused to hire an outside investigator to determine who knew about Lauer’s misbehavior.