The 27-year-old American actress and 34-year-old actor from Northern Ireland attended the Los Angeles premiere of their movie Fifty Shades Darker at the Ace Hotel.
Johnson turned heads in a blush-colored Valentino dress with a plunging neckline and back, while Dornan looked dapper in a navy suit with a striped tie and tan shoes.
"I think we were kind of forced into being best friends," the actress said in an interview with the Today show at the event. "Thank God, because if we didn't get along, it would be really, really awful."
"It's a very unique sort of friendship. It's a friendship that's built on maybe more trust than other friendships need to be because of the situations we had to get through together," Dornan added of the film series' many sex scenes.
The Fifty Shades movies are based on the E.L. James erotic book trilogy of the same name. The series follows the romance between Anastasia Steele (Johnson), an inexperienced college student, and Christian Grey (Dornan), a BDSM-loving businessman.
Fifty Shades Darker, which opens Feb. 10, was preceded by Fifty Shades of Grey, and will be followed by Fifty Shades Freed in 2018. Johnson laughed through a Fifty Shades skit this week on The Tonight Show, and Dornan recreated Christian's workout routine on Conan.