The 26-year-old forward has been frozen out of things at Parc des Princes and has been looking to leave the capital for some time.
PSG boss Luis Fernandez has been reluctant to allow Leroy to leave but the player has finally got his wish.
Bottom side Troyes will have the services of Leroy for the remainder of the season, but he is still looking forward to returning to PSG despite his joy at getting the chance for regular football.
"I met the Troyes officials on Wednesday and they convinced me," said Leroy.
"I still had two trails, Le Havre and Troyes, which were the two clubs ready to pay my wages.
"It is a good solution to come here, both for me and for PSG - I wanted to be loaned.
"When I come back to Paris in June, I hope to feel well. I hope to come back at my best."
Leroy will join PSG team-mate Selim Benachour at the club, as the Tunisian has already moved to Troyes on loan.
Meanwhile, Moroccan defender Talal El-Karkouri has told Luis Fernandez that he wants to leave the club.
El-Karkouri has rarely played for PSG and already asked to leave in the summer, when he had contact with Bolton, West Ham and Birmingham, although he has no concrete offers this winter.
