The 37-year-old announced back in April that he will be returning to his native Brazil to see out the remainder of his career after 17 years in Europe.
Fernandinho initially left Paranaense in 2005 for an eight-year spell at Ukrainian side Shakhtar Donetsk, where he won the Ukraine top flight six times as well as the UEFA Cup in 2009.
Fernandinho joined Manchester City in the summer of 2013, spending nine seasons with the Citizens.
The former Brazil international was a faithful servant at the Etihad Stadium, winning five Premier League titles, six League cups and one FA Cup.
He also made 383 appearances in total for Pep Guardiola's side and scored 25 goals.
"We had numerous proposals, from several different clubs, from Brazil and abroad," said Fernandinho at his unveiling.
"But the most sensible decision was to return home and try to deliver my best here at Athletico now.
"Establish a brand that will end my career playing for just three clubs: two in Europe and one in Brazil. I'm very happy, I thank my family, which has always supported me in this decision.
"Not only my heart, but all of us ended up speaking louder at that moment."
Athletico Paranaense are currently managed by former Chelsea, Portugal and Brazil manager Luiz Felipe Scolari.
