The couple met on the set of the director's new film 'Wall Street: Money Never Sleeps' and has joked they have him to thank for their romance.
He said: "It was all thanks to me! I was thrilled when I realised they were going to be an item. It just made their scenes together all the better - especially the love scenes. Let's just say it was no stretch for them!"
Shia and Carey, who were first linked in August last year, didn't let their blossoming romance distract them from the task of reviving the themes first depicted in 80s Hollywood classic 'Wall Street' for the sequel.
Stone said: "They were completely professional on the set, but there was no mistaking what was happening. You could see their chemistry right away, and it was pretty powerful."
The acclaimed filmmaker spoke about Shia and Carey's relationship at a Cannes party on Friday (14.05.10), where the couple were reportedly inseparable as they partied with Michael Douglas and Josh Brolin, who also star in the highly anticipated movie sequel.
Shia and his new girlfriend have so far kept quiet about their relationship, though the 'Transformers' hunk has said: "It works out. It's not like we're the premiere couple - we're not the red carpet king and Queen."
'Wall Street: Money Never Sleeps' will get its cinema release in September.