Hilton, 29, pleaded guilty this week to misdemeanor drug possession in Las Vegas. The charge stemmed from her arrest last month.
E! News said she was detained Tuesday at Tokyo's Narita International Airport and questioned by immigration officials for more than 6 hours about her U.S. arrest before they banned her from entering the country.
"I'm really tired," E! quoted Hilton as saying. "I'm going back home, and I look forward to coming back to Japan in the future."
"Paris is very disappointed and fought hard to keep her business commitments and see her fans, but she is forced to postpone her commitments in Asia," Hilton's publicist, Dawn Miller, added. "Paris understands and respects the rules and laws of the immigration authorities in Japan and fully wishes to cooperate with them. Paris looks forward to returning in the future to a country she loves and has been coming to for the past 10 years."
Hilton was scheduled to make personal appearances in Tokyo Wednesday, then in Kuala Lumpur, Malaysia, and Jakarta, Indonesia, later this week.