The judge ruled he could remain free pending an appeal.
Lula has rejected claims that he received an apartment as a bribe in a corruption scandal linked to state oil company Petrobras.
He says the trial is politically motivated and has strongly denied any wrongdoing.
The case is the first of five charges against him.
Lula served eight years as president until 2011 and has expressed interest in running again in next year's elections for the left-wing Workers' Party.
On Wednesday, a judge found him guilty of accepting bribes from engineering firm OAS in the form of a beachfront apartment in return for his help in winning contracts with the state oil company.
In a statement, Lula's lawyers insisted he was innocent and said they would appeal.
"For more than three years Lula has been subject to a politically motivated investigation. No credible evidence of guilt has been produced, and overwhelming proof of his innocence blatantly ignored," they wrote.
The head of the Workers' Party, Senator Gleisi Hoffmann, also hit out at the ruling, saying it was designed to stop Lula standing for office.
She said the party would protest against the decision.
In theory, Lula is free to run in the presidential election until the legal process ends.
The BBC's Katy Watson in Rio says he remains a popular politician and the sentence will deeply divide Brazil.