The incident occurred at about 2:34 p.m. at a store in the 1100-block of West Jefferson Street, Shorewood police said.
Police said a driver backed up through the whole storefront, injuring a UPS worker inside.
The employee was transported to St. Joseph Medical Center and was responsive, but her condition was not immediately known, police said.
The driver of the car was transported to St. Joseph Medical Center with minor injuries and a passenger was evaluated at the scene, police said.