Nanofiltration (NF) has been applied for treating arsenic contamination of groundwater from an area located in the Sila Massif in Calabria (Italy). High values of As in different environmental matrices, such as rocks, soils and waters, were observed. In fact, the geochemical analysis of 3 groundwaters (GWs) samples collected show As values which exceeded the permitted levels of 10 µg L−1. The Arsenic is present mainly in the pentavalent form (As(V)). Different types of NF membranes, operating conditions and the competing effects of different ions with Arsenic in the GWs samples have been evaluated for analyzing their effect on the arsenic removal.