The pot, which has a street value of $290,000-$300,000 was sent to the City Blue store on 69th Street.
"In this particular case, we get a legitimate store employee almost have a heart attack when he sees what's delivered and he calls police right away,"said Supt. Michael Chitwood, Upper Darby Police.
Authorities say the sender, from California, made the same mistake twice.
First 60 pounds of pot was sent via FedEx on Tuesday then another 30 pounds was sent on Wednesday.
"Somebody is missing a lot of marijuana," said Supt. Chitwood.
Police know who the drugs were addressed to and are now working to locate that person.
With the marijuana now in the hands of police, investigators suspect the costly mistake will put a dent in drug sales here.
"It's the Christmas season, more and more packages are being delivered so more and more attempts are being made to deliver whether it's cocaine, heroin and marijuana," said Supt. Chitwood.
As police search for the package's recipient here, they are consulting with authorities in California to catch the person who sent it.