The Sydney Morning Herald claims Harrelson let the secret slip at the Santa Barbara International Film Festival on Tuesday.
He was there to present his No Country for Old Men co-star with the Montecito Award for his contribution to film when he confirmed the two Spanish actors were an item.
Penelope Cruz and Javier Bardem have previously denied rumours they are more than just co-stars. (photo: agencies via China Daily)
He said: "I can't believe the luck Javier has. If you look at his biography-one page is just describing his journey and then the second page is all of the awards he's won.
"And not to mention, I found this out last night too-he's going out with Penelope Cruz!"
At the mention of Cruz, the crowd cheered while an embarrassed Javier, 38, put his head in his hands.
(Agencies via China Daily February 3, 2008)
