The cause of death was said to be "pulmonary embolism".
Montcourt, ranked no.119 in the world was reported found dead by his girlfriend in front of the door to his ground floor apartment in the Paris suburb of Boulogne-Billancourt on Monday night.
"The French Tennis Federation (FFT) is literally in shock on learning of the death of Mathieu Montcourt," a Federation statement said.Montcourt's last tournament was in the Croatian town of Rijeka late June where he reached the semi-final of a Challenger Tour event.
"His sudden loss plunges the whole tennis family into immense sadness," the statement added.
FFT technical director Patrice Dominguez said: "Mathieu was a young and promising talent who was really on the way up. "He was a hard-working, serious and clean-living lad. We are devastated and our first thoughts are with his family."
His career was badly hit in August last year when he was banned for eight weeks and fined 12,000 dollars for betting on the Internet on the outcome of tennis matches.
Initial autopsy results indicate Montcourt died of cardiac arrest, according to French police.
"Based on preliminary findings, we conclude the death was from natural causes. We are awaiting the toxicology results, which should be available next week, to be completely certain," a police source told AFP.(Via pr-inside.com, AFP)