There were reportedly so many pills in the box that she said they were spilling out of the bag they were packaged in.
Choosing to stay anonymous, the woman - from Rock Hill, South Carolina - was expecting her package on Sunday but was given a box stuffed with oxycodone pills.
A woman in SC got quite a surprise after opening a package she thought contained a yoga mat she had ordered, but found almost 20,000 illegal pills valued at $400,000 instead.
Brown said they found there were two bags of about 10,000 pills each.
"Most of this is counterfeit", said Marvin Brown with the York County drug unit.
The woman told police that she did not know who had used her name and address.
Instead, it was a heavy box filled with $400,000 worth of illegal oxycodone.
Drug unit Commander Marvin Brown said the package was likely meant to be delivered to the woman's previous address, which she recently moved from and is now vacant, WSOC reported.
He continued by saying the sender may have meant to send the package to the woman's former address at a empty condo in the area.
"The dealers weren't as intelligent as they thought they were", Commander Brown added. He said unwitting people find that those in the drug trade use fake or wrong addresses and names, then wait for packages to be delivered. Officers are now trying to figure out where the package was supposed to go.
The woman, who did not want to be identified, quickly called police and reported the illegal shipment.