The two have been married since 2006 and share five children together.
In a since-deleted post, McDermott took to social media to share the news in a statement on Saturday.
"It’s with great sadness and a very very heavy heart that after 18 years together and 5 amazing children, that @torispelling and I have decided to go our separate ways, and start a new journey of our own," the actor's statement read. "We will continue to work together as loving parents and guide and love our children through this difficult time. We ask that you all respect our privacy as we take this time to surround our family with love and work our way through this. Thank you all for your support and kindness. 🙏.
McDermott's post led with a throwback picture of him and the Beverly Hills 90210 actress and ended with a recent picture of them posing with four of their kids.
The 50-year-old actress and the 56-year-old actor, who share five kids together, have been married since 2006.
A source tells ET that the couple seemed to be in a better spot as they were celebrating their daughter's birthday.
"Tori and Dean seemed to be in a much better place as of last weekend," the source says. "They are being respectful of each other and listening to one another more after many hard times and sometimes difficult exchanges. With that being said, they have realized that it was finally time, and both were ready. They feel like their kids are healthy, safe, and good, and now they need to move on. They are trying to move forward as amicably as possible."
Spelling has yet to break her silence. McDermott's statement comes after Spelling shared a family picture by the pool featuring her, McDermott and their five children.
"Back to my zip code… @beverlyhilton hotel has been such a huge part of my life. Went there with my family growing up and now I’m lucky enough to be able to take my own family. #beverlyhitonhotel gave us the most wonderful experience for @stella_mcdermott08 15th birthday," she wrote. "Penthouse suite, cabanas, cakes, the works. Tbh it was hard to leave 😂. Family time is the best time and @beverlyhilton you continue to always make us feel like true family. We love you! xoxo #90210."
Spelling and McDermott share their children Finn, 10, Stella, 15, Liam, 16, Hattie, 11, and Beau, 6. McDermott also has a son, Jack, from a previous relationship. The split news come after a source told ET in November that the two were "very much struggling" in their marriage.
"Tori and Dean do things as a family for the sake of their kids and live in the same house but sleep in separate rooms," the source said. "Tori is more vocal about what goes on between them, and Dean is just completely checked out."
According to the source, McDermott's continued alleged infidelities have hurt the marriage most.
"Dean has been caught in so many lies and infidelities over the years and Tori is just over it," the source said. "Dean does not want to get divorced because of financial reasons, and Tori doesn't want to for the sake of their family."
"Tori isn't dating anyone else, and they are trying to figure out the next steps," the source added.
In November, Spelling shared her family holiday card which pointedly didn't include McDermott, although she later told a fan in the comments section that he was filming in Canada.
McDermott has previously admitted to cheating on Spelling. Multiple outlets reported in 2013 that he cheated with actress Emily Goodhand, while they were both filming Chopped Canada.
Spelling and McDermott were both married to other people when they first began seeing each other. In a 2014 episode of her reality show, True Tori, she said they slept together the first night they met while filming the Lifetime TV movie Mind Over Murder in 2005. At the time, she was married to her first husband, Charlie Shanian, and he was married to his first wife, Mary Jane Eustace.
"Maybe I have a hard time with that part [blaming Goodhand] because that's how I met Dean," she said on the show while discussing her husband's infidelity. "I mean, he was married. ... We had sex the first night we met."
"It wasn't like, 'oh, just get your rocks off, have sex with someone just to have sex,' you know?" she continued. "It was a conscious decision, like, fell head over heels for you."
In 2019, McDermott talked about cheating on his wife on his Daddy Issues podcast.
"I really, really wish that I had been given the knowledge of thinking with your head, not your penis," he said. "Because I did a lot of thinking with my penis."
"I've been there. I've cheated and it's so not about the person you're with," he also shared. "For me, it wasn't about T, it was about inadequacies with myself. I felt so bad about myself, I felt like a piece of s**t, I needed to do that to feel some kind of power."
In June 2021, Spelling acknowledged that she and McDermott no longer sleep in the same room.
"You know what, right now my kids and dogs sleep in my bed," Spelling said during her appearance on SiriusXM Radio Andy's Jeff Lewis Live. "[Dean's] in a room. Since he left, this is not good, you guys. But since he left, he was gone for six months filming in another country. They all stayed with me. So, I currently still have four in the bedroom with me who have yet to go back to their rooms. They have beds in there and two sleep in bed with me. And pets. Three dogs."