With a return address in Japan, the turtles were individually wrapped in nylon stockings to provide warmth and ventilation, then placed inside a cardboard box.
The animals were identified as Japanese pond turtles. Though not yet endangered, the species has been experiencing a decline in population due to loss of natural habitat.
Authorities believe the turtles were being shipped to China because of the country's growing demand for exotic pets.
Quarantine officials said that the turtles would be either returned or destroyed.
In 2010, a Shanghai zoo complained that it had no more space for exotic animals abandoned by the city's petowners, the Telegraph reported. The zoo demanded owners think carefully before buying such animals.
Just last month, China's Chongqing airport police seized 10 bear paws during a routine check, according to Shanghaiist.