Kaka was officially presented as a Real Madrid player in front of around 50,000 fans in a Hollywood-style show at the Bernabeu on Tuesday.
Director general Jorge Valdano had promised president Florentino Perez's second spell at the helm would be a "super-production" and they did not disappoint with the presentation of their first signing.
"It is a very special day for me. I hope I can write my name in the club's history books with victories and conquests," a slightly overawed Kaka said from a stage on the pitch.
The doors of the stadium had been thrown open to the public who packed the stands around a stage decorated with the club's nine European Cups.
Perez was up first, greeted with chants from the fans as he thanked Kaka for choosing Real Madrid before the Brazilian was given a pop star welcome and emerged to roars from the crowd.
The Brazilian playmaker was presented with the number eight shirt and had to be protected by bodyguards as he walked around the pitch to greet fans.
Some of them jumped over the barriers and tried to touch the former AC Milan player who cost Real 67 million euros.
The event was covered live on television and internet websites across the world.
Spain defender Raul Albiol, who joined for a reported fee of 15 million euros from Valencia, is expected to be presented later this week.
Portugal winger Cristiano Ronaldo, who was signed from Manchester United for 80 million pounds ($132.7 million), will take the stage on Monday.