"There are still parts of my game I can work on," said Retallick, who has developed from a hard-hitter in the engine room to being able to direct the point of the All Blacks' attack with his precise passing game.
Asked what role Whitelock had played in his development, Retallick replied: "Everyone in this All Black team is pushing each other to try to get better. We talk about having the two best XVs in the world. If you're not playing one week you're trying to better each other and drive a good performance. He's played a huge role.
"It's a huge honour to receive the award. It's something I didn't think about until last week when I was nominated.
Watch: All Blacks: Retallick World Rugby Player of the Year
"I just wanted to improve on the previous couple of years. Obviously I didn't think it would go this well."
World Rugby chairman Bernard Lapasset said: "Brodie Retallick has been at the heart of another hugely successful year for the All Blacks with his superb lineout skills, ball-carrying ability and work at the breakdown playing a huge role in a June series win against England, the Rugby Championship title and a strong November series."
The All Blacks also won team of the year.
Other top ABs
IRB player of year - previous All Black winners
Kieran Read (2013)
Dan Carter (2005 and 2012)
Richie McCaw (2006, 2009 and 2010)