The man, whose identity has not been revealed, told the police that he lives at a Boston shelter.
He found the backpack, that also contained passports and 'personal papers' at South Bay Mall in Dorchester.
The man flagged down officers and told them he found the black backpack in front of the mall, 'The Boston Herald' reported.
Police said that in addition to USD 2,400 in US currency and USD 39,500 in American Express Travelers Cheques, the backpack contained passports "and various personal papers."
The rightful owner was identified by his Chinese passport and the property was returned to him, police said.