Dassault can appeal against the sentence and so is unlikely to have to give up his seat in the French Senate, where he represents the mainstream right Republicans party whose presidential candidate, François Fillon, faces his own troubles, before the next election in 2017.
At 91, he is the oldest member of the Senate and his age saved him from going to jail, even though the size of the fraud and the length of time it continued would have merited imprisonment in the judges' view.
Millions hidden in Liechtenstein and Luxembourg
Dassault, who was ranked France's fifth-richest man in 2016 by Challenges magazine, was found to have hidden millions of euros from the tax authorities over 15 years in accounts in Liechtenstein and Luxembourg, including 31 million euros in 2006 and nearly 12 million in 2014.
He also omitted to declare 16 million euros of property on his 2011 tax declaration and 11 million euros in 2014.
Since the fraud was discovered, the millionaire aeronautics boss has paid 19 million euros in back taxes, a fact that his lawyers argued should weigh in his favour.They also claimed that he had inherited the tax-dodging system from his father, Marcel, who hid his money because "he was frightened of going through another war" and wanted to "protect his family".
Serge Dassault did not appear in court during the trial.
Vote-buying inquiry still ongoing
The Dassault dynasty is one France's wealthiest and most influential families.
One of its companies, industrial software maker Dassault Systèmes, announced an 11 percent rise in profits to 447.2 million euros on Thursday.
As well as owning one of the world's biggest manufacturers of military, regional, and business jets, it owns France's biggest-selling newspaper, Le Figaro, which is firmly on the right of the political spectrum.
Referring to an article in the paper signed by Dassault that touched on France's public deficit, prosecutor Ulrika Delaunay-Weiss commented that, while he had "so many ideas to straighten out public finance, he does not mention tax fraud".
Dassault has been banned from public office before - for one year due to illegal gifts of cash during the 2008 local elections in Corbeil-Essonnes, a Paris suburb where he is mayor.
The tax evasion came to light during an inquiry into alleged vote-buying in the town in 2009-10.
That case is still under investigation.