Real Madrid goalkeeper Casillas, 31, and Barcelona playmaker Xavi, 32, have helped Spain to consecutive European Championship triumphs with a World Cup in between, the country's first, and were put forward for the award by FIFA president Sepp Blatter.
They have been friends since they competed together at the Under-20 World Cup in 1999 despite playing for bitter club rivals Real and Barca and the jury said that was one of the reasons they had been selected.
Their friendship had "helped resolve disputes between players of different clubs, promoting fair play and the philosophy of the team as the basis for sporting success," the jury wrote.
"It's true that there was tension at times but friendship comes before everything else," Xavi said on the sidelines of Spain's training camp in Madrid after learning of the award.
"It's recognition of our work but also of this generation of players, some of whom have been friends for 15 years," he added.
Blatter said the award reflected the "fantastic work" done in Spain's academies, both at club level and with the national teams.
"It's something that goes beyond what they have achieved in football," he said, in an interview with Spanish sports daily Marca published on Wednesday.
"Casillas and Xavi are an example on the field of play but also as people when they are away from pitch."
Previous winners of the award include Sebastian Coe (1987), Seve Ballesteros (1989), Steffi Graf (1999), Lance Armstrong (2000) and Rafael Nadal (2008).
The Spanish team won it in 2010 following their World Cup victory in South Africa.
The award will be presented next month by Spain's Prince Felipe and his wife Princess Letizia. Recipients receive a representative sculpture by Spanish artist Joan Miro and 50,000 euros.