Pato, who joined the club world champions from AC Milan for a Brazilian record transfer fee of 15 million euros last month, came on in the second half and scored Corinthians' fifth goal.
"It was a special day because I managed to play [for the first time] after 70 days," the 23-year-old, who was plagued by injuries in his time in Serie A, told reporters.
"And to close with a 5-0 result was very special. To come here and play with the world champions is a great privilege," added Pato, who returned home looking to reclaim a place in the Brazil team for the 2014 World Cup.
In the Minas Gerais championship, Cruzeiro beat city rivals Atletico Mineiro 2-1 at the Mineirao stadium in the state capital Belo Horizonte.
It was the first match in the Mineirao since it was closed in June 2010 for World Cup refurbishments and the first time fans of both teams had attended the derby since then, with 62,000 spectators packed in on Sunday.
While the Mineirao, which will hold three matches in the Confederations Cup in June and six during the World Cup, was undergoing work, the derby was played at various smaller grounds without visiting supporters for security reasons.
Atletico, last season's Brazilian championship runners-up and captained by Ronaldinho, were favourites to win the opening match of the Mineiro championship.
But they were upset by a Cruzeiro team under a new coach and featuring eight changes from the side they fielded for their last match in the 2012 Brazilian championship.
Anselmo Ramon had the honour of scoring the first goal in the renewed stadium when he put Atletico ahead with a 23rd minute header.
Araujo equalised five minutes later from Ronaldinho's cross into the box before substitute striker Dagoberto marked his debut for Cruzeiro by heading the winner in the 62nd minute.
The Mineirao and Arena Castelao in the northern city of Fortaleza are the only two stadiums of the six chosen for June's Confederations Cup to be ready, with FIFA renewing pressure on Brazil to speed up their preparations for the tournament
Internacional, trained by former Brazil coach Dunga, beat arch-rivals Gremio 2-1 in the Porto Alegre derby in the Gaucho (Rio Grande do Sul) championship.
