"It's been a few months," an insider told Us in the May 15 issue.
Minka posted a photo with Jesse in January of this year as they worked on the untitled project.
The rumored couple went to catch a movie Monday night in West Hollywood.
They were both sporting ball caps, and Jesse added a hoodie as they left the theater.
After he announced he was splitting with his wife of 13 years Aryn Drake-Lee in April 2017, rumours circulated that Jesse and Minka were 'definitely' seeing each other.
Neither have commented on speculation over whether their relationship has progressed in any way from a professional one.