The 33-year-old British actor and 26-year-old American actress were spotted kissing in the rain while filming the Fifty Shades of Grey sequel in Vancouver, B.C.
Dornan and Johnson play Christian Grey and Anastasia Steele, respectively, in the Fifty Shades film adaptations. Sources reported the pair, who shared several steamy scenes in the first movie, burst out laughing after their kiss on set.
The Fifty Shades movies are based on E.L. James' book trilogy of the same name. Fifty Shades of Grey opened in theaters in 2015, with Fifty Shades Darker to follow Feb. 10, 2017. The third installment, Fifty Shades Freed, will open Feb. 9, 2018.
"I'm looking forward to embodying Christian again -- and getting a chance to show more of him," Dornan told People magazine in November.
Fifty Shades follows the romance between Christian, a BDSM-loving businessman, and Ana, a sexually inexperienced college student. The first movie earned $571 million at the box office but swept the Razzie Awards for bad films on Saturday.
Fifty Shades Darker will co-star Luke Grimes as Christian's brother Elliot, with Kim Basinger and Bella Heathcote as his former lovers, Elena Lincoln and Leila Williams. Arielle Kebbel and Tyler Hoechlin will play Gia Matteo and Boyce Fox.