Earlier reports said the duo had separated but the actors put the rumours to rest after they were pictured walking hand-in-hand in New York, reported Us magazine.
Despite their relationship going strong, sources said that Gosling isn't ready to take the next step - moving in with Mendes.
"He says he wants to slow down and not live with her yet. But he doesn't want to lose her," a source said.
The news of the romance first broke in September when "The Place Beyond the Pines" co-stars were photographed on an adorable, PDA-packed visit to Disneyland.
Mendes was next seen with Gosling to Thailand, where he shot "Only God Forgives", where she also cooked him meals.