Brolin: I'm in love with Winslet
The 46-year-old actor admitted he fell in love with the Oscar-winning actress, who is married to Ned Rocknroll, as they worked together on Labor Day.
"A lot of times with chemistry, if you have chemistry with somebody, it can actually work against you. When you don't like an actor, it can actually work for you because there's more electricity there," he said.
" I really like Kate a lot and it scared me. The fact that it was so easy with her and yet, for some reason, we still had a lot of electricity every day between us."
He added: "She knows that I'm in love with her and have been and will ever be. And so does Ned by the way! He knows it too and he's OK with it."
Josh, who plays convict Frank Chambers in Jason Reitman's drama, also joked that he went behind bars for his research.
"I went to jail a couple of times," he quipped before quickly saying: "No. It became more instinctual when we were on the set and my relationship with Kate became much more necessary than I thought."
The Men In Black 3 actor admitted Kate was the only person he and Jason wanted for the role of depressed single mum Adele Wheeler, and they waited patiently until she was available.
"Jason and I were both very keen on Kate. She couldn't do it right away so we had to wait. We ended up doing a movie separately - he did Young Adult and I did Men In Black 3 - until Kate was available and said yes and voila!"
:: Labor Day opens in cinemas on March 21.