Pato, who has also enjoyed time at Corinthians, Chelsea and Villareal, signed a three-year contract with Sao Paulo. It will be his second spell at the club.
Pato, 29, broke into the Internacional side as a teenager in 2006 and helped them to the Club World Cup the same year when they beat Barcelona 1-0.
His pace, maturity and cool head in front of goal won him a transfer to AC Milan, where he spent five years.
However, he has failed to make a lasting mark at any of the six clubs he graced since and fallen out of favour at international level, with his last cap coming in 2013.
(Reporting by Andrew Downie; editing by Sudipto Ganguly)
