Naomi Watts and Billy Crudup are in the "early stages" of dating.
The 'Gypsy' star's romance with her co-star is reportedly going well and the pair are said to be "very into each other".
A source told Us Weekly magazine: "Naomi and Billy are dating, but in the early stages. They're very into each other."
The pair first fuelled speculation they were dating when they were spotted holding hands in Tribeca, New York, in mid-July.
A fellow diner at the place they were having lunch said at the time: "Naomi Watts and Billy Crudup walked in holding hands. We didn't know they were a couple. Pretty cool seeing two big stars so into each other. [They] looked happy and were laughing a lot, then left again holding hands."
It came just two months after Naomi admitted dating wasn't "really in her world right now".
Speaking about Liev Schreiber, her former partner of 11 years, she said: "We have huge love and respect for one another and high hopes for it to remain that way going forward. [Dating] just seems completely frivolous and counterproductive and just not really in my world right now.
"There are good days and bad days and Liev and I are on great terms and we're trying to do our absolute best for the sake of the children and we hope to keep moving forward in that way."
Meanwhile, Naomi - who has sons Samuel, eight, and Alexander, 10, with Liev - split from the actor back in September 2016, when they issued a joint statement to confirm they had gone their separate ways.
They said: "Over the past few months we've come to the conclusion that the best way forward for us as a family is to separate as a couple.
"It is with great love, respect and friendship in our hearts that we look forward to raising our children together and exploring this new phase of our relationship. While we appreciate your curiosity and support, we ask the press to be mindful of our children and respect their right to privacy."