The couple are currently promoting their hard-hitting crime drama The Place Beyond The Pines, the film which brought them together in November 2011.
In the movie, Notebook heart-throb Ryan plays a motorcycle stunt rider-turned bank robber alongside girlfriend Eva, who takes the role of his love interest and mother of his child.
The pair left their intense roles behind as they each stepped out in stylish outfits at the film fest.
Eva, 39, wowed the crowd with monochrome glamour, teaming a black silk headband with a black-and-white lace Dolce and Gabbana dress, white earrings and black stilettos.
Canadian-born Ryan, 31, - known for his quicky style - wore a double breasted Gucci suit and button down collared shirt.
The duo's co-star Bradley Cooper embraced Ryan, an old friend, as he joined them.
Bradley, whose character in the film is a cop-turned-politician, looked dapper in a navy blue suit.
The Hunger Games star Jennifer Lawrence, who reportedly begins filming the film's sequel next week was also out at the festival, showing off her new brunette locks.
Promoting her new movie The Silver Linings Playbook, in which Bradley also stars, the 22-year-old, wore a dark blue dress and pronounced black eye make-up to the premiere.