The charges against American Julie Hamp came after customs agents last week found 57 tablets containing oxycodone in a parcel sent to her, according to reports by the Asahi newspaper and public broadcaster NHK.
Hamp, 55, said she did not believe she was committing a crime, the reports said.
Police and Toyota both declined to comment today.
Hamp was promoted to head of communications for the auto giant after previously working at Toyota's North American division.