He wasn't aware but at the time, the "Avengers" star's second marriage –to French businessman Romain Dauriac– was dissolving. They married in 2014 and share a 5-year-old daughter, Rose. Before that, Johansson was married to Ryan Reynolds from 2008 to 2011.
"It felt fated in a way," Johansson told reporters at the Venice Film Festival on Thursday. "It came somehow at just the right time."
The 34-year-old stars alongside Adam Driver in the Netflix film, "Marriage Story," about a couple — she plays an actress and he plays a theater director — with an 8-year-old son managing a bi-coastal separation and divorce. It premiered on Thursday night at the festival and is competing for the Golden Lion award.
Colin Jost (L) and Scarlett Johansson attend the premiere of "Avengers: Endgame" in April. (Jeff Kravitz/FilmMagic)
Although Johansson had her own experiences to draw on, she said there was something of everyone behind the film in the brutally honest but tender character study.
Baumbach wrote the script knowing that Driver and Johansson would play the couple. He said he realized in the writing process that, "Through a divorce we could explore a marriage."
"Although they're coming apart, love always exists," he said. "It's in every scene, it's there."
Romain Dauriac (L) and Scarlett Johansson in April 2017. (Rabbani and Solimene Photography/Getty Images)
Laura Dern, who plays Johansson's divorce lawyer, added that it personifies "the business of divorce."
One scene, in which the two leads have a particularly traumatic fight, had audiences at the Venice Film Festival buzzing. Driver said he didn't really analyze it afterward, but that it was two "pretty difficult" days. Baumbach added that it was "harrowing" and they'd often have to stop for a break, with the actors either going to their rooms or taking a walk around the block to regroup.
"They would run the whole scene almost every time. It was like watching two of the best athletes compete," Baumbach said. "In many ways, it was one of the most rewarding experiences I've had as a director."
"Marriage Story" will make stops at the Telluride and Toronto Film Festivals before hitting theaters on Nov. 6, followed by its Netflix debut on Dec. 6.
The Associated Press contributed to this report.