The Fiat 500L car was used by Pope Francis during his trip to the US last year for the World Meeting of Families.
Michael and Kate Chapman, owners of Chapman Auto Group, secured the winning bid of $82,000 (around £58,000) at Philadelphia Auto Show's black-tie event.
The family plan to put the black Fiat on display at their dealership in Horsham.
The second Fiat used by the pontiff will be displayed during the Philadelphia Auto Show, which runs until the end of next week.
Kenneth Gavin, Archdiocese of Philadelphia spokesperson, said more than 19 bidders from across the US took part in the 11-minute auction for the car.
Money from the sale will go towards a number of charities and the archdiocese's special education schools.
Donna Crilley Farrell, executive director of the World Meeting of Families, said: "We are so heartened by the fact that this extraordinary gift will go on to enrich the lives of so many individuals."
