Alexandre started playing futsal at the age of 4. His ability soon became known all around the south Brazilian state of Parana. After being praised by many of his managers, the teenager went to Porto Alegre, Rio Grande do Sul, to try out for Internacional. In 2001, at the age of 11, he moved there and started sharing housing with 83 other teenagers that, much like him, wanted to make a name for themselves in the Internacional first team.
In 2000, when Alexandre was 10 years old, x-rays from a broken bone revealed that he had a tumor in his arm. The doctors realized that the tumor would become cancerous in two months if not removed. Alexandre’s family could not afford the surgery to remove the tumor, but the doctor, Paulo Roberto Mussi, was a family friend, and operated for free. This event was particularly significant because it occurred in a very crucial year when Alexandre was working towards a professional career with Internacional.
He adopted the nickname Alexandre Pato (“Alex the Duck”), after the city where he was born.
Pato began his playing career at Internacional in Porto Alegre, where he played for both the youth and senior teams between 2001 and 2007. On his first team debut, at the age of 17, Pato helped Internacional to a 4-1 win over Palmeiras on November 26, 2006. He had created three of the goals and scored the other goal.
Pato scored Internacional’s second goal of the 2006 FIFA Club World Cup on December 13 in the semi-final game against Al-Ahly Cairo, helping the team win 2–1 and a spot in the final. With this goal, Pato took Pele’s record as youngest scorer in the history of official FIFA competitions (17 years and 102 days, against Pele’s 17 years and 239 in the 1958 FIFA World Cup against Wales). He was substituted in the final of the competition, before team-mate Adriano Gabiru scored the winner, ensuring the title for Internacional.
Pato was linked to several high profile clubs including Benfica, Juventus, Inter, Chelsea and Arsenal.
Incumbent European champions A.C. Milan officially confirmed the signing of Pato on August 2, 2007. He stated before that Ronaldo and Kaka are his idols. The transfer fee paid amounts to the minimum fee clause in Pato’s contract with SC Internacional for €22 million. His debut was a dream come true for young Alexandre Pato, scoring his first AC Milan goal at the San Siro.
Due to Italian football regulations regarding non-EU minors, Pato was unable to play official matches for Milan until January 3, 2008, when the Italian transfer window and registration reopened. However, AC Milan was allowed to include the player in friendlies and training beginning September 3, 2007, one day after his 18th birthday. Pato made his non-competitive debut in a 2–2 draw against Dynamo Kiev on September 7, 2007 and scored a header. on January 4, 2008, Pato’s transfer to Milan became official.
Pato scored his first Milan goal in his Serie A debut against S.S.C. Napoli in a 5–2 home victory on January 13, 2008. He scored his first brace for Milan in a 2–0 victory over Genoa C.F.C. in San Siro on January 27, 2008.
He helped Brazil win the 2007 South American Youth Championship, which qualified the country for the 2007 FIFA U-20 World Cup, and has been selected by Dunga for the 2008 Summer Olympics.
He scored his first goal for the senior team on his debut against Sweden at the Emirates Stadium on March 26, 2008.