The court in Chambéry in southeastern France also put them under electronic surveillance for a six-month period, which it said could be extended.
Mastro, 87, and his 63-year-old wife Linda were detained in October in Annecy in the French Alps following an international arrest warrant.
The Seattle-based Mastro had a $2-billion empire that fell apart after the real-estate crash. He declared bankruptcy and claimed more than $250 million in debts.
The couple are accused of trying to hide their assets from creditors, according to the Seattle Times.
They moved out of their lavish California mansion and fled in June 2011 after a judge ordered them to hand over two massive diamond rings belonging to Linda Mastro and costing more than $1 million (€770,000) each.
"My aim was to get them out of prison before Christmas," their lawyer Thomas Terrier said. "I'm very happy."