Authorities detected the weapon inside the man's carry-on items at a security checkpoint.
Officers say it was sitting among some clothing and was not loaded.
When asked about it, the man reportedly told officials that he received the pistol as a gift from his father.
The man -- who is from Middletown, Pennsylvania -- was charged with a criminal citation and was fined.
So far this year, TSA has caught 15 guns at Philadelphia International Airport.