Pierre Le Guennec, 77, who worked for Picasso in 1970-73, and his wife, Danielle, on Friday lost their appeal against the sentence first passed on them by a lower court in 2015.
The court in the southern city rejected their claim that Picasso's widow, Jacqueline, gave them the artworks and found them guilty of being in possession of stolen goods.
It also ordered them to give the works to Picasso's son, Claude, who is head of the Picasso Foundation.
Officials put the works' value at 60-100 million euros.
The couple claimed that they had not even looked at the artworks until 2009-2010 when they asked Picasso's heirs to establish the authenticity of 180 pieces and a sketchbook containing 91 drawings.
The heirs declared that they were genuine and had been executed between 1900 and 1932 and had not been in the inventory made at the artist's death in 1973.
After the court's judgement, Claude Picasso's lawyer, Jean-Jacques Neuer, accused the couple of manipulating the art market, pointing out that the works were in perfect condition, and claimed this was only the "tip of the iceberg".