The 87-year old has had two years of the sentence suspended for his part in corruption and money-laundering charges linked to the Russian doping scandal, including allowing athletes suspected of doping to cover up test results and continue competing.
His age means that he is unlikely to go to jail, with presiding judge Rose-Marie Hunault telling him that he could expect conditional release and a fine of $582,000.
Diack had been under house arrest for almost four years while French authorities investigated claims that he had taken $3.5 million in payments to conceal cheating.
Responding to a verdict that concluded his actions had “undermined the values of athletics and the fight against doping”, the Senegalese’s lawyers vowed to appeal against the “unfair and inhumane” punishment.
He was a key figure in world sport during his 16-year presidency of the federations until his replacement by Briton Lord Coe in August 2015.
Diack’s son, Papa Massata Diack, received five years in prison and a fine of more than $1.1 million, having been banned for life from athletics in 2016.
Russian coach Alexei Melnikov also earned a three-year sentence, while Valentin Balakhnichev received two years and a fine of $2.3 million.
The Diacks are also being investigated on corruption charges relating to the awarding of the 2016 Olympic Games to Rio de Janeiro and the postponed 2020 Games to Tokyo.
The ruling awarded World Athletics around $18.6 million in damages.