The laundry service is in Rome's Trastevere tourist district, which already has as homeless shelter and has a tradition of helping the poor.
The facility is run by volunteers and provides six washing and machines plus driers and irons. There are plans to also provide showers, a hairdresser, clinic and a distribution point for basic goods, the Office of Papal Charities said in a statement.
A statement from the Vatican said Pope Francis wanted to offer a "concrete" example of the papal jubilee Year of Mercy.
The pontiff has previously shared a birthday dinner with the local homeless community and offered them private tours of the Sistine Chapel as well as practical assistance such as handing out sleeping bags during a cold snap in the capital.
Volunteer barbers give free shaves and haircuts every Monday - an initiative which is set to be expanded in other Italian cities - and toilets and showers were installed near the Vatican for the homeless living in the tiny city-state.
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Photo: Vincenzo Pinto/AFP