Da Silva, who is universally known as Lula, tweeted "Lula Free" with a video of himself working out and lifting weights in a gym inside the prison, where he has been detained since April 2018.
When released, Lula would be free to engage in politics but would not be eligible under Brazil's Clean Record law to seek elected office for eight years after his first conviction, which was in June 2017. Per a Supreme Court determination in 2016, criminals whose convictions were upheld on appeal could begin serving their sentences. He was favoured to win the 2018 presidential election, but his imprisonment barred him from running.
Venezuelan President Nicolás Maduro is celebrating former Brazilian President Luiz Inácio Lula da Silva's release from jail as a step toward rebuilding unity in South America.
Now, Lula can remain free as long as appeals of his corruption conviction unfold.
Da Silva presided over a period of rapid growth fueled by a commodities boom that expanded the country's middle class. This suggests that Lula, and potentially thousands of other prisoners, could be freed. His impassioned oratory can just as easily elicit laughter or tears from those among his supporters.
Lula's release is likely to spur the divided and rudderless left and, paradoxically, could also help Bolsonaro, who capitalized in last year's vote on widespread anti-PT sentiment after a massive corruption scandal.
Da Silva was expected to give an address Saturday at the headquarters of the Metalworkers' Union near Sao Paulo.
Left-leaning supporters hailed the release of their standard-bearer, but want more and are now advocating for his name to be cleared. The case is related to the alleged purchase of a beachfront apartment in Sao Paulo state.
There are several other ongoing cases against the former President, who was in office from 2003 to 2010 and a key figure the election of Dilma Rousseff, his handpicked successor, for another two terms. Da Silva stands accused of corruption, though he and his supporters call the charges politically motivated.
Rosangela da Silva was a weekly visitor at the facility, though Lula reportedly complained that the couple - friends since the 1990s - were not given conjugal rights.
Later this month, the Supreme Court is due to consider whether the judge who jailed him, Sergio Moro, was unbiased. Brazil's top court has reached a narrow decision that could release nearly 5,000 inmates that are still appealing their convictions, including Da Silva. Protests supporting Moro and his anti-corruption crusade have been scheduled this weekend in major Brazilian cities.