The pontiff made a surprise visit on Friday to a safe house run by the Catholic organisation, the Pope John XXIII Community, for people rescued from forced prostitution.
It's understood his unexpected arrival prompted tears of joy among the women, who were each around 30-years-old and come from countries including Nigeria, Romania and Albania.
As part of The Extraordinary Jubilee of Mercy year of prayer held by the Roman Catholic Church, the Pope has visited a number of community groups as part of his Fridays of Mercy initiative.
The Pope John XXIII Community is said to currently have 400 currently under it's care, while the organisation has helped more than 7,000 women and girls over the last 25 years.
According to the Walk Free organisation, 45.8m people around the world are victims of slavery.
A major conference trying to eradicate human trafficking was held by the Vatican at the United Nations headquarters in New York in May 2016.