Diack, 87, was found guilty of taking bribes from athletes in return for orchestrating the cover up of test results that enabled them to continue competing, including in the 2012 London Olympics.
Diack was also found guilty of accepting Russian money to help finance Macky Sall's 2012 presidential campaign in Senegal, his home country, in exchange for slowing anti-doping procedures, the court ruled.
The court had heard how Diack solicited bribes totaling 3.45 million euros ($4.1 million) from athletes suspected of drugs cheating and paid off other officials at the International Association of Athletics Federations to aid with the cover up.
The presiding judge said the former long-jumper's actions had "undermined the values of athletics and the fight against doping."
The court handed Diack a four-year prison sentence, two years of which are suspended, and imposed the maximum fine of 500,000 euros ($594,000).
Diack's lawyers called the judgment against him unfair and inhumane, and said they would appeal.
One of the civil parties in the case, French marathon runner Christelle Daunay, said she was relieved after jearing the court read out the verdict. Daunay had accused the IAAF of protecting athletes like Russian long-distance runner Liliya Shubukova, who was later suspended for doping. She said the suspension had come too late, and athletes like her were robbed of a podium finish, and the prize money that went with it.
Diack was once one of the most influential men in the sport, leading the IAAF, now known as World Athletics, from 1999 to 2015.