Greene, 24, beat Puerto Rico’s Javier Culson and this year’s fastest man, United States’ Bershawn Jackson, at the IAAF Continental Cup in Split, Croatia.
Swansea Harrier Greene went under 48 seconds for the first time, clocking 47.88 to beat the stadium record.
Greene now has Commonwealth Games gold in Delhi in October in his sights.
He also has his sights on the 47.82s UK record of Kriss Akabusi in his sights, having beaten his stadium record in Split and become the first Briton to go under 48 seconds in 18 years.
Greene beat fellow Welshman Rhys Williams into second place at last month’s European Championships in Barcelona and says his training has improved since then.
“If anything my training has been getting even better since Barcelona,” he said.
“When I felt Jackson go past me so soon, I felt annoyed, but I had a feeling the race would pan out like that because he’s done that several times throughout the season.
“I just tried to stick to my own race and when I changed down my stride pattern I felt really smooth.
“I’ve been fighting for a time like that all season, and it came when I least expected it.” – BBC