The Django Unchained star fuelled rumours that he was dating the Australian actress after he was spotted leaving her apartment building in the morning, reported the New York Post.
But the actor's spokesperson insisted: "That didn't happen. Leo worked late and stayed home."
She later joined him in Las Vegas for his 38th birthday, where an eyewitness said: "There looks to be some strong chemistry between Leo and his leading lady. They spent a lot of time at the party together."