Aziz, who ruled the pivotal country between North Africa and sub-Saharan Africa between 2008 and 2019, fell into disgrace under successor and current President Mohamed Ould Ghazouani, a former political ally.
The former president had been on trial since January alongside 10 other prominent figures -- including two former prime ministers -- for illicit enrichment, abuse of functions, influence-peddling and laundering.
He was convicted of illicit enrichment and laundering but cleared of the other charges.
The court also ordered the confiscation of Aziz's illicitly acquired assets.
The 66-year-old former head of state did not react to the judgement.
Aziz has been in detention since January 24, having also spent several months in prison in 2021.
He received the longest sentence of all the defendants in the trial, with two former prime ministers and two former ministers cleared of the charges.
"The trial we attended was a political trial, and its verdict is also very political," one of Aziz's lawyers, Mohameden Ould Icheddou, said.
Another of his lawyers announced their intention to appeal against the verdict.
But a state lawyer, Brahim Ould Ebetti, told AFP that the verdict was "very lenient."
Prosecutions of former heads of state are rare in the world, but especially so in Africa. Most former leaders brought to national or international courts are tried for blood crimes rather than corruption.
'Victim of a plot'
A trader's son who came to power in a bloodless coup, Aziz stepped down in 2019 after two terms in which he defused a jihadist insurgency that has swept across other countries in the Sahel.
He was succeeded by his former right-hand man, Mohamed Ould Ghazouani, in the first peaceful transfer of power between elected leaders in the history of a country marked by coups and upheaval.
But relations soured within months of the handover as allegations emerged of financial misconduct.
The graft inquiry began shortly after he left office, starting with a parliamentary probe in August 2020.
The probe focused on Mauritania's oil revenues during his presidency, the sale of state assets, the winding up of a public company in charge of food supplies and the activities of a Chinese fishing company.
Aziz, who was accused of piling up an estimated $72 million, said he was the victim of score-settling by rivals and persistently refused to speak to the examining magistrate.
He told a Nouakchott court in April that "these charges are baseless and you have no proof of any of this."
"I am the victim of a plot by those I opposed," Aziz said after the court read out the charges against him.
In the final moments of his trial, the former president implicated his successor by claiming that Ghazouani had given him two suitcases filled with several million euros (dollars) the day after his election in 2019.
Mauritania ranked 130th out of 180 in the 2022 Corruption Perceptions Index by the organisation Transparency International.
NOUAKCHOTT - A court in Mauritania's capital Nouakchott on Monday sentenced former president Mohamed Ould Abdel Aziz to five years in prison for having abused his position to amass an ill-gotten fortune.