Isco, whose contract with Real expired in June, has put pen-to-paper on a two-year deal with Sevilla.
Isco, 30, will be reunited with former Spain and Real Madrid manager Julen Lopetegui at Sevilla.
"I'm 30 years old, I'm in the prime of life, I feel young and that I have many joys to give," he said. "I understand that there are doubts about my past few years, where I've been unable or have not been allowed to play as I wanted.
"Now it's my turn to dispel those doubts and send them a message of calmmess. I'm going to give it my all and show the level that I think I've never lost. I'll take care of dispelling those doubts."
The midfielder, who has played 38 times for Spain, will be eager to revive his career, having been a fringe player at Madrid in recent seasons.
"I am very happy and excited about this new chapter," Isco said. "I know where I am coming from and hopefully, we can do great things this year. I really want to show the level I have and that I have never lost. I come to a team where I know the coach and the players."
Isco joined Madrid in a €30 million deal from Malaga in 2013 and went on to win five Champions League trophies, three La Liga titles and one Copa del Rey in his nine-year spell at the club.
He made 17 appearances for Carlo Ancelotti's side last season, only starting three matches.
Sevilla finished fourth in LaLiga last season and will play in the Champions League this campaign.
"It's a team with a style of play that I love and hopefully we can win titles," Isco said. "I've chosen Sevilla among the many offers I have because from a sporting level is what interested me the most.
"It's a team that competes, that wants to play football well, plays in the Champions League, a club that is constantly growing... It's the best team to show my football again. I want to keep winning and that's why I'm here."
Isco could make his Sevilla debut on Friday when the Andalusian side visit Osasuna in their league opener.