Ricardo Izecson dos Santos Leite was born in Gama, Federal District, to Simone dos Santos, an elementary school teacher, and Bosco Izecson Pereira Leite, a civil engineer.
Kaká began his career with São Paulo at the age of eight.
At the age of 18, Kaká suffered a career-threatening and possibly paralysis-inducing spinal fracture as a result of a swimming pool accident, but made a full recovery. He attributes his recovery to God and has since tithed his income to his church.
He made his senior side debut on 1 February 2001 and scored 12 goals in 27 appearances, in addition to leading São Paulo to its first and only Torneio Rio-São Paulo championship, in which he scored two goals in two minutes as a substitute against Botafogo in the final, which São Paulo won 2–1.
He made his debut for the senior Brazil squad in a friendly match against Bolivia on 31 January 2002.
Kaka won World Cup 2002
His Serie A debut was in a 2–0 win over Ancona. He scored ten goals in 30 appearances that season, also providing several important assists, such as the cross which led to Shevchenko's title-deciding headed goal, as Milan won the Scudetto and the UEFA Super Cup, whilst finishing as runner up in the Intercontinental Cup and the 2003 Supercoppa Italiana.
The steady European interest in Kaká culminated in his signing with the European champions, Italian club A.C. Milan, in 2003 for a fee of reported €8.5 million, described in retrospect as "peanuts" by club owner Silvio Berlusconi. Within a month, he cracked the starting lineup, replacing Rui Costa in the attacking midfield playmaking position, behind strikers Jon Dahl Tomasson, Filippo Inzaghi and Andriy Shevchenko.
On 9 April 2006, he scored his first Rossoneri hat-trick against Chievo, with all three goals scored in the second half.
On 2 November 2006, he scored his first Champions League hat-trick in a 4–1 group stage win over the Belgian side Anderlecht.
Kaká won the Champions League title when Milan defeated Liverpool 2–1 on 23 May 2007, avenging the previous loss on penalties two years before.
On 30 August, Kaká was named by UEFA as both the top forward of the 2006–07 Champions League season and UEFA Club Footballer of the Year, as well as being named as part of the UEFA Team of the Year for the second time.
Milan began its 2007–08 season by winning the UEFA Super Cup on 31 August, defeating Sevilla 3–1, with Kaká scoring the third goal.
He played his 200th career match with Milan in a 1–1 home draw with Catania on 30 September, scoring from a penalty
On 5 October, he was named the 2006–07 FIFPro World Player of the Year, and was elected as part of the FIFPro World XI for the second time in his career.
On 2 December 2007, Kaká became the eighth Milan player to win the Ballon d'Or, as he finished with a decisive 444 votes, well ahead of runner-up Cristiano Ronaldo.
On 16 December, Kaká won the FIFA Club World Cup against Boca Juniors, scoring Milan's third goal of the match in a 4–2 victory which allowed them to be crowned World Champions.
On 17 December, Kaká was voted the 2007 FIFA World Player of the Year with 1,047 votes, ahead of Lionel Messi with 504 and Cristiano Ronaldo with 426.
In January 2008, Kaká was also named the 2007 Serie A Footballer of the Year, winning the award for the second time in his career.
He signed a contract extension through 2013 with Milan on 29 February 2008.
On 14 October, he cast his footprints into the Estádio do Maracanã's sidewalk of fame, in a section dedicated to the memory of the country's top players.
BBC reported on 13 January 2009 that Manchester City made a bid for Kaká for over £100 million.
On 19 January, Silvio Berlusconi announced that Manchester City had officially ended their bid after a discussion between the clubs, and that Kaká would remain with Milan.
On 3 June 2009, it was reported that newly elected Real Madrid president Florentino Pérez had offered to buy Kaká from Milan for a reported €68.5 million.
On 8 June, Milan and Real Madrid confirmed Kaká's move to the Santiago Bernabéu Stadium on a six-year deal for €67 million fee.
Kaká was unveiled as a Real Madrid player on 30 June 2009.
He scored his first goal for Madrid during a pre-season match on 19 August 2009, in a 5–0 victory against Borussia Dortmund.
Kaká later made his league debut in Madrid on 29 August 2009 in a 3–2 win against Deportivo de La Coruña.
On 5 August 2010, Real Madrid announced that Kaká had undergone a successful surgery on a long-standing left knee injury and would face up to four months on the sidelines.
In March 2011, Kaká suffered from Iliotibial band syndrome, which kept him sidelined for a few weeks.
Real Madrid began the 2012–13 season by winning the Supercopa de España against rivals Barça.
On 4 December 2012, after scoring in a 4–1 win against Ajax, Kaká became the top Brazilian goalscorer in Champions League history, with 28 goals.
On 29 August 2013, Kaká expressed his desire to leave Real Madrid, having scored 29 goals and provided 32 assists in 120 appearances in all competitions over four seasons at the club.
Milan confirmed that Kaká would join the club on 2 September 2013 from Real Madrid on a free transfer with only performance-related incentives owed to Madrid; after agreeing to personal terms, he signed a two-year contract.
On 29 March 2014, Kaká scored twice in a 3–0 win against Chievo, his 300th match for Milan.
On 30 June 2014, Kaká had his Milan contract terminated through mutual consent despite having a year remaining, by activating a release clause as a result of the team not qualifying for European competitions.
On 3 July 2014, Kaká arrived at São Paulo and began training the next day.
Kaka joined future MLS franchise Orlando City as their first Designated Player.
On 8 March 2015, Kaká scored a free kick for the equaliser in a 1–1 draw on his MLS debut against New York City FC at the Citrus Bowl, the first in Orlando City's competitive history.
Kaká announced his retirement on 17 December 2017, after turning down offers from former clubs São Paulo and Milan. He also expressed interest in working as a director, confirming that his former club Milan had offered him a role.