The 30-year-old has already attained legendary status at the club and has been an ever-present figure for the Spanish giants since breaking into the senior ranks in 1999.
He has since won among others, four La Liga titles and two Champions League crowns - in addition to the World Cup and European Championship successes with Spain.
Speaking of his ambitions and plans for the future, Casillas insists he is not finished with winning titles.
"I want to continue to win titles," he told the club's website. "I would like a fifth league trophy, a second Copa del Rey title and another World Cup ...
"That is my ambition. If I ever feel tired or no longer as excited as I am now I will let others take over with hopes of their own.
"The keys to winning titles are ambition, drive and hope. First, one is very demanding with oneself individually, and then collectively. I advise kids who want this to fight for their dreams.
"As a child I hoped to be Real Madrid's goalkeeper and I made it. What matters is that they have that drive."