The couple began dating more than five years ago after meeting at a Las Vegas party. In the ensuing years, they have been rumoured to have split and reconciled on numerous occasions.
A source has now told The New York Post's Page Six that DiCaprio and Refaeli "are going through a difficult patch", but are still committed to working through their troubles.
While both stars were in New York City on Monday night, they attended separate events.
Refaeli was present at the Metropolitan Museum of Art's MET Ball, while DiCaprio chose to spend an evening with friends at the city's famed Standard Hotel.
A rep for DiCaprio declined to comment on the actor's personal life, while Refaeli's spokesperson could not be reached.
Late last year, it was reported that the Inception star was considering converting to Judaism for the Israeli model.
