Representatives for the actors did not respond to request for comment yet, reported People.
This will be the second child for the pair, who already have a 19-month-old daughter Esmeralda Amada.
The duo began dating in 2011 after meeting on the set of "The Place Beyond the Pines", in which they played parents.
Gosling, 35, and Mendes, 42, had managed to keep their first pregnancy a secret for several months.