Cahuzac resigned in 2013 after becoming a source of huge embarrassment to then president Hollande given that the minister's job was to crack down on tax dodgers.
A plastic surgeon before entering politics, Cahuzac was found guilty in 2016 of funnelling cash into a Swiss bank account from the lucrative hair transplant clinic he ran with his ex-wife.
The 65-year-old appealed his three-year sentence, prompting a full re-trial that could see Cahuzac risk up to five years in prison and a 375,000 euro fine.
His former wife Patricia Menard, who held an account in the Isle of Man that was also used in the fraud, was sentenced to two years in prison.
In France sentences of this length are not usually served behind bars -- instead via an electronic bracelet or other curtailments on a person's liberty.
Cahuzac, a rising Socialist star who was well respected across the political spectrum, initially denied having a Swiss account after investigative journalism outlet Mediapart reported it in 2012.
Footage of him lying to parliament was repeated in an endless loop on TV news channels after he finally confessed in April 2013, "consumed by remorse", to having the account.