The FIFA Technical Study Group picked the Real Madrid shot-stopper after some outstanding performances which inspired Spain to win their first-ever World Cup trophy.
Previous winners of this award are Gianluigi Buffon (Italy) in 2006, Oliver Khan (Germany) 2002 and Fabien Barthez (France) in 1998.
The 29-year-old Casillas made several saves against the Netherlands in Sunday's final, which his side won 1-0. One of the saves was a point-blank block which denied Arjen Robben, who was clean on goal.
He also saved a penalty against Paraguay in a quarter-final match as Spain won 2-1 to reach the last four.
Casillas made history when he became the first goalkeeper since Italy's Dino Zoff in 1982 to lead a team to World Cup glory.