Among the Waldensens living in Northern Italy and Southern France, the dissimulation of their faith is one of the most peculiar characteristics of the daily religious practice during the late Middle Ages. Such behavior was the byproduct of the persecutions and anti-heretical campaigns of the xiv and xv centuries. Building on the most recent documentary and archival sources and findings, the essay offers a long term historical analysis of the use of nicodemism among the Waldensens of Southern Italy, namely of Calabria and Puglia, between mid-xvi and end of xvii centuries.  The essay also focuses on the repressive practices enacted by the Roman Inquisition in such context, from the initial field investigations, to the 1561 slaughter and the instrumental use of the accusation of religious simulation during the course of the xvii century.