A panel of four justices unanimously backed the conviction on Tuesday, issuing a prison sentence of four years and two months to the former lawmaker, who now risks arrest on return to Brazil.
Eduardo Bolsonaro, who has argued in Washington that he and his family are the target of unfair persecution by Brazil's Supreme Court, said he had not been properly notified about the court's legal process.
The office of Brazil's Prosecutor General had charged him with courting US authorities to help his father's case by imposing sanctions on the court's justices and tariffs on Brazilian goods last year.
Both the tariffs and the sanctions were later scaled back.
The younger Bolsonaro moved to the US in 2025, months before the trial that ultimately convicted his father of plotting a coup to overthrow the results of the 2022 election he lost.
The former lawmaker has said his efforts in Washington were not aimed at getting his father acquitted but at forcing Brazil's Supreme Court to punish officials who, in his account, were not complying with Brazil's constitution.
More recently, Eduardo Bolsonaro has thrown his support behind his brother Senator Flavio Bolsonaro's presidential run.
Both met with US President Donald Trump in the White House last month.
Polls show that the senator is the strongest challenger to President Luiz Inacio Lula da Silva ahead of an October election.
Jair Bolsonaro was Brazil's president from 2019 to 2022.
He is serving a 27-year sentence under house arrest due to health issues.
Tuesday's ruling makes Eduardo Bolsonaro ineligible for eight years to run for public office in Brazil.
The lower house of Brazil's Congress had already removed him from its ranks and stripped his lawmaker's salary in December after he missed more than a third of the deliberative sessions in 2025.
Eduardo Bolsonaro said in his statement that the real motive of the trial was to bar him from public office.
