Last month, the England Sports Writers Association chose Diaz as England’s Player of the Year after he performed well in his first season after joining from Benfica last year.
Diaz played a prominent role in City winning the English Premier League title for the third time in four seasons, in addition to winning the League Cup.
In the title race, Diaz beat several prominent names, including Kevin De Bruyne, Bruno Fernandes, Jack Grealish, Harry Kane, Mohamed Salah and Mason Mount.
Diaz is the fourth player to be voted Player of the Season by fans, the leaders of the 20 Premier League teams and a panel of experts.
The previous three winners are Manchester United’s Nemanja Vidic, former Manchester City captain Vincent Kompany and Liverpool’s Virgil van Dijk.
Portuguese Cristiano Ronaldo won the award for the best player in the Premier League season with Manchester United twice in the 2006-2007 and 2007-2008 seasons.