Heavy Rain creator David Cage has predicted that the PS3 title will sell 1.5 million by the end of 2010.
Speaking to German site Play3, Cage said: "We have sold more than 1 million copies of Heavy Rain worldwide.
"That was a surprise to many, since estimated sales were between 200,000 to 300,000 units. We estimate that by the end of the year, we will have sold 1.5 million copies, and are very pleased with the reception."
Heavy Rain was released back in February. It's already topped a million sales, topping the UK charts along the way.
Cage recently called the success of the unorthodox Heavy Rain "a message to the industry".