The plane - belonging to Cameroon airline CamAir-Co - touched down on Monday morning at Roissy-Charles de Gaulle airport after a long flight from the African country's capital Yaounde.
"While checking over the plane, we noticed the presence of a man, quite young, of African origin, unidentified, who had died in the landing gear," a source close to the case said.
"One of the theories is that he froze to death," she added.
Another source said an autopsy would be done on Tuesday, adding that the victim looked like he was "15 to 17 years old."
This is not the first time that stowaways have died in a bid to get to France, but such an incident had not happened at the Paris airport in at least three years.