Former Burundi leader Domitien Ndayizeye and four others have been acquitted on charges of plotting to assassinate the president.
President Domitien Ndayizeye (l) handed over power last August
Two others were convicted and sentenced to 15 and 20 years in prison.
Mr Ndayizeye was leader under a power-sharing agreement intended to end years of ethnic conflict, before stepping down in 2005 after elections.
Diplomats criticised Mr Ndayizeye's arrest. The man convicted of organising the plot had alleged he was tortured.
Ex-rebel leader Alain Mugabarabona was sentenced to serve 20 years in prison.
Last August, he told local radio stations by phone from his prison cell that he was threatened with death.
"This coup story has been invented by the Documentation Nationale," said Mr Mugabarabona , referring to Burundi's powerful presidential police and intelligence service.
"Everything I accused former President Domitien Ndayizeye, former Vice-President Alphonse-Marie Kadege and the others of was extorted by torture and threats," said the official of the rebel National Liberation Forces (FNL).
Mr Ndayizeye was succeeded by Pierre Nkurunziza, a former rebel leader who was elected by a landslide.