The `Dick Tracy` actor was previously believed to have struggled to deal with his daughter Kathlyn transitioning into a man named Stephen, but to show his support for him he and wife Annette Benning took their family out for a dinner at Il Covo restaurant in Hollywood.
A source told National Enquirer magazine: "The dinner was an unofficial public display that he`s proud of his family, especially Stephen, for having the courage to be who he truly is.
"It wasn`t easy for Warren. But he learned a lot about the transgender community over the past year.
"Warren even made an emotional toast to Stephen during the dinner and said he was proud to have such a brave son."
However, Warren does continue to make mistakes when it comes to addressing his son.
The source added: "Warren never stopped loving his child, but he had plenty of issues and fears to overcome.
"The bottom line is he missed his little girl. But he`s finally resigned himself to the fact that one day Stephen will probably have gender reassignment surgery and legally become a boy.
"Warren still slips up and calls Stephen `her` or by his birth name Kathlyn, but the bottom line is he`s totally onboard with his child`s new lifestyle."