A source tells ET that the former couple was 'having issues' ahead of their split.
One source tells ET, "Jodie and Joshua's hectic work schedules started to weigh on their relationship starting over a year ago, when they were both filming projects and not always in the same place."
The source adds that the pair "tried to make things work, and were taking steps to help their relationship and deal with managing their busy schedules."
News of the breakup appeared to come as a surprise even to those close to the stars.
"From an outside perspective, things looked great for a while," the source shares. "But privately, they were slowly growing apart."
On Monday, Turner-Smith filed for divorce from the Dawson's Creek alum after three years of marriage, citing "irreconcilable differences." She listed the date of separation as Sept. 13 and is seeking joint custody of their three-year-old daughter, Juno Rose Diana Jackson.
"They are trying to be amicable as they move forward with their divorce and trying to avoid any feelings of animosity," the source continues. "They're both respectful of each other and focused on co-parenting their daughter. They want to have a positive relationship for her sake and for themselves."
On Monday, after Turner-Smith's divorce filing, a source told ET: "Jodie and Joshua have been having issues lately. They celebrated Jodie’s birthday on Sept. 9 at The Flower Shop in NYC, but arrived separately and left separately. It was a big party and they were distant throughout the night and barely around each other. Jodie spent the majority of the evening downstairs."
Rumors of a rift between the 45-year-old Fatal Attraction star and the 37-year-old Murder Mystery 2 actress surfaced last September, when eagle-eyed fans reportedly noted that the stars had appeared to unfollow -- and then re-follow -- each other on Instagram. Just two months later, they were seen walking arm-in-arm at an after-party for The Fashion Awards in London, England.
In March, Jackson had his arm wrapped around Turner-Smith as they posed for photos at the 2023 Vanity Fair Oscar Party in Beverly Hills, California. At one point, Turner-Smith even reached up and interlaced her fingers with Jackson's.
But their body language appeared cooler during their last public outing together, as they attended the unveiling of the new fully electric Lotus Emeya on Sept. 7 in New York City. The event served as something of a birthday celebration for Turner-Smith, with Jackson presenting her with a cake as photographers looked on.
Just last week, Turner-Smith stepped out solo for the Clooney Foundation For Justice's 2nd annual Albie Awards in New York City -- where she did not address her husband's absence.
"It's so nice to be back, it's such a beautiful event," she told ET on the red carpet. "I'm really, really happy to be here."
After their initial meeting in 2018, Turner-Smith previously said that neither party expected their relationship to last very long. During an interview on Late Night With Seth Meyers in May 2021, she revealed that the pair had a one-night stand that evolved into a "three-year one-night stand."
Although the duo was seen in public several times in 2018, they finally made their red carpet debut while attending the Queen & Slim premiere at 2019's AFI Fest at the TCL Chinese Theatre in Hollywood.
ET spoke with Jackson during a press junket for his show, Dr. Death, in July 2021, and he shared how his life had changed "in every single possible way" since tying the knot and becoming a father over the previous year.
"There is nothing that is not better off than being married to her and having that baby. It's everything," he said at the time.