Augustin Ngirabatware, the planning minister when 800,000 people, mostly ethnic Tutus, were massacred in 1994, was convicted of genocide and incitement to genocide, CNN reported.
He was also found guilty of raping a woman repeatedly, being involved in a roadblock as Tutsis were tracked down, and distributing weapons.
Ngirabatware has been in the custody of the U.N. International Criminal Tribunal for Rwanda since 2009. He was arrested in Germany in 2007.
Justice Hassan Bubacar Jallow, the tribunal's chief prosecutor, said Thursday 83 of the 93 people indicted in connection with the genocide have been arrested and 75 have been tried during the past 18 years.
The tribunal has obtained 65 convictions, while 10 defendants were acquitted. Three people are known to have died, 10 cases have been transferred to national courts and a few of those indicted are fugitives.
"The delivery of judgment today in this case marks a historic occasion and important milestone in the work of the International Criminal Tribunal for Rwanda," Jallow said.