A native of S„o Carlos, he received his nickname NenÍ (Portuguese for baby) because he was the youngest in both his family and his group of childhood friends. Like most Brazilian children, he started out playing soccer, and was good enough to receive some interest from professional clubs. He did not play basketball until he was 14, but apparently took to the game quickly. His original basketball teacher claims that when he first tried to dunk, he not only dunked the ball, but destroyed the basket.
He first came to international attention at the 2001 Goodwill Games as a member of the Brazilian national team. Afterwards, he excelled at the NBA's Chicago predraft camp in 2002; the New York Knicks picked him seventh overall in the 2002 NBA Draft and immediately traded him to the Denver Nuggets.
He began the 2002-03 season on the bench, but ended it as a starter, averaging 10.5 points, 6.1 rebounds, and 1.6 steals, and finishing in the league's top ten in shooting percentage (.516). After the season, he was selected to the NBA All-Rookie first team.
In the 2003 offseason, he legally changed his name to his lifelong nickname of NenÍ.