The Spain international was keen to lavish praise on his new club after criticizing los Blancos in an interview four years ago.
The 21-year-old attacking midfielder, who will wear the No.23 jersey, the same number David Beckham wore when he joined Madrid 10 years ago, says he chose the shirt because it was his brother's birthday.
Isco had infamously stated four years ago that he had little love for Madrid, a club he labelled as "arrogant", but at Wednesday's unveiling, he had nothing but praise for los Blancos.
"First of all, I want to thank the efforts of the president [Florentino Perez], my family, and love of all the fans," the former Malaga man told reporters. "For a player there is nothing greater than being at Real Madrid; it is the ultimate. I hope to enjoy it a lot here, and delight everyone, winning many titles for Real Madrid.
"It is curious to be presented with the same number and on the same day that Beckham was. I had several shirts available, but I chose the 23 because it is the day of my brother's birthday."
Perez, for his part, was keen to give Isco a warm welcome to the Bernabeu, admitting Madrid was delighted that it had topped competition from Manchester City for one of the most highly rated young players in Europe.
"Isco had offers from other clubs, but he has chosen to play for Real Madrid," the Blancos supremo said.
"Isco is joining a club that doesn't know the word impossible. This is your stadium and your home. Welcome to Real Madrid."
Isco came through the youth team ranks at Valencia before becoming a star during his two-year stay at Malaga.