Shannen Doherty's Ex, Kurt Iswarienko, Denies Affair, But She Vows 'Truth Matters'

Shannen Doherty and her estranged husband have a much different memory of how and when they split up -- his version flies in the face of the infidelity she alleged on her podcast, but Shannen is doubling down on "the truth."

Here's the deal ... Shannen made headlines last week when she went on her new 'Let's Be Clear' podcast and claimed she had surgery to remove a brain tumor right after learning Kurt Iswarienko "had been carrying on an affair for two years," and their 11-year marriage was "essentially over."

Sources close to Kurt are disputing Shannen's narrative, telling TMZ ... Kurt and Shannen had actually been living separate lives for 2 years before her January 2023 surgery, and he had been upfront about starting a new relationship with someone else while they were living in different states.

On her podcast, Shannen said ... "I went into that surgery early in the morning and I went in after I found out that my marriage was essentially over ... I felt so betrayed.”

However, our sources say Kurt told Shannen of his new relationship just after New Year's of 2023. We're told Shannen fell a few days after Kurt told her about the other woman, and that's when she was sent for an MRI, doctors discovered her brain tumor and then she had the surgery.

Shannen's fully shooting down that version of events -- Tuesday night, on her Instagram, she called it "an absolute lie" and accused people connected to Kurt of trying to skirt the truth.

The sources close to Kurt say he'd been living in Texas, and Shannen was in California, when doctors found the tumor. but he flew back and went with her to doctor appointments ... only for her to tell him the morning of the surgery she didn't want him there.

Our sources say Shannen making it seem like Kurt had been sneaking around her back isn't accurate, but obviously, the timing was pretty rough.

TMZ broke the story ... Shannen filed for divorce in April, when her rep, Leslie Sloane, told us, "Divorce is the last thing Shannen wanted. Unfortunately, she felt she was left with no other option. You can contact Kurt's agent, Collier Grimm at PICTUREKID as she is intimately involved."

BTW ... the new woman Kurt revealed to Shannen was indeed Collier, and we're told they're still together.

Shannen and Kurt tied the knot way back in 2011, and she was diagnosed with cancer in 2015 ... with our sources telling us he was there for her throughout all of her early diagnosis, treatments and doctor visits.

We're told Shannen's treatments worked at first, but the cancer came back and by late 2020 their marriage was not working ... with the COVID pandemic playing a role.

Our sources say Kurt still wanted to be part of her life, and was renting homes in her area from January 2021 to July 2021 while they tried to figure things out -- but when they couldn't, he moved to Austin, and ultimately met Collier.