Shantia Dennis, 26, was arrested Wednesday by an undercover officer who discovered the alleged scheme, CNN reported.
Customers looking to buy heroin were told to go through the drive-through and say "I'd like to buy a toy," said a statement from Mike Manko, communications director for the Allegheny County District Attorney's Office.
Buyers then pulled up to the first window, where they were handed a Happy Meal box containing heroin, the statement said.
When the undercover officer carried out the drug buy, he recovered 10 stamp bags of heroin inside of a Happy Meal box, the statement said. Officers recovered 50 more bags of heroin, as well as some marijuana, from inside the restaurant, Manko said.
Dennis was arrested at the scene and charged with two counts of possession, one count of criminal use of a communication facility, one count of prohibited acts of delivery and one count of possession with intent to deliver, CNN reported.
Authorities said the heroin being sold at Dennis' McDonald's was not related to potentially lethal batches of heroin being sold in Western Pennsylvania.