Police said the man found the teeth Saturday when he unzipped a compartment in the wallet. One tooth had a filling.
The customer turned the wallet and the teeth over to employees but left the store without giving his name.
Police investigating the incident told The Cape Cod Times that the teeth belong to an adult, but since there was no blood or gum tissue on the teeth, they would be unable to perform DNA tests.
A Walmart spokeswoman said the company believes it was an "isolated incident," but will investigate.