The incident was reported around 9:30 a.m. in the 1000 block of Nester Place in the Bustleton neighborhood.
The victim told police that a man, dressed in a full postal uniform and wearing a safari hat, knocked on her door and said he had a package that she needed to sign for.
The man then forced his way inside the home with a gun, police said, demanding money and jewelry.
During the robbery, police said, the gunman received a phone call - which he answered.
"As the complainant was giving him her jewelry, he ran out of the house," said Det. Stephen Dewey of the Philadelphia Police.
The suspect then got away with approximately $2,300 in cash and an undetermined amount of jewelry.
The victim was not harmed.
The victim's family is baffled as to why someone might target their loved one, saying she is not wealthy, or a store owner.
The only thing they could think of: three days ago the victim won about $2,300 at a local casino.
Sgt. Dewey says people need to be vigilant before allowing someone they don't know in their home. Whether they are a mail carrier or utility worker, ask for official ID.
"If you still don't believe the person is who they say they are, call 911 and have the police come out and investigate," Dewey said.