Someone found the wallet and handed it to police, who traced it to the 357-pound wrestler because of an identification card inside, said the official, who declined to give her name citing agency policy.
The 20-year-old Gagloev told police he had received the marijuana from a foreigner in Roppongi - a Tokyo district famous for its bars, clubs and raucous nightlife.
Gagloev faces up to five yeas in prison with forced labor and could be deported with no possibility of re-entry. He also could be thrown out of the sumo federation.