The 28-year-old BlacKkKlansman actress was spotted shopping in Paris, France, with the 47-year-old Maniac star on Monday.
Harrier sported an all-red ensemble, including capri pants, a cardigan top and a matching jacket. She paired the look with circular shades and black flats while carrying a bag from French beauty store Biologique Recherché.
Theroux also went casual for the shopping trip, stepping out in black jeans, boots and an army green bomber jacket.
The pair didn’t show any PDA, but stayed close as they walked around the city.
This isn’t the first time Theroux has been spotted out with Harrier. Back in May, the hunky actor was seen frolicking in the ocean in the south of France with the actress aboard a yacht.
At the time, a source told ET, “Justin is not in a relationship. He’s super social and loves meeting new people and collaborating on ideas with friends.”
Theroux and his estranged wife, Jennifer Aniston, called it quits in February after two years of marriage. Theroux recently opened up to The New York Times about the split for the first time.
"The good news is that was probably the most -- I'm choosing my words really carefully -- it was kind of the most gentle separation, in that there was no animosity," he said. "In a weird way, just sort of navigating the inevitable perception of it is the exhausting part."