Paris-based Prince Karim, the 75-year-old head of the 15 million-strong Ismaili Muslim community, divorced his second wife, German singer Gabriele Thyssen, in 2004 and a French court awarded her the sum in September.
But he has now appealed the settlement to France's Court of Cassation, the country's highest court, the judicial source told AFP.
Thyssen, who had married the Aga Khan in 2000, had won the settlement in an appeal court after an initial ruling awarded her only €12 million. She had been demanding a €200 million settlement.
The Aga Khan's fortune is estimated at €10 billion and he is well-known for his thoroughbred racing and breeding operations.
During the divorce case, French judges had difficulty estimating his wealth as he enjoys a rare fiscal privilege that allows him to pay taxes in Switzerland despite living in France.