The jury said that both athletes "symbolise the values of friendship and camaraderie that go far beyond the rivalry of their respective teams.
Casillas said: "We are talking about a prestigious award that honors the work of athletes who have had very good careers. To tell the truth, I think that Xavi and I receive this award as a reflection of our maturity and careers in which along the way we have achieved great things both personally and as team members, with Real Madrid and the Spanish national team.
"It is a little bit of everything coming together. I am grateful that in this case an agreement was reached on two important players in the past decade of Spanish football, who represent two great clubs, Barcelona and Real Madrid, and the Spanish national team. I am grateful to the people who voted and who opted for this joint candidacy for the Prince of Asturias Award."