The pope made the appeal during his traditional Sunday prayer on the U.N.'s world day against trafficking.
Francis said "every year, thousands of men, women and children are innocent victims of labor exploitation, and sex and organ trafficking." He added that it has become something considered normal: "This is ugly. It is cruel. It is criminal."
He called on the world to renew its commitment to battling "this abhorrent plague, a form of modern slavery," and to pray that traffickers "change their hearts."
The International Labor Organization estimates 21 million people are victims globally of forced labor, including victims of human trafficking for labor and sexual exploitation.