The present research evaluates the groundwater nitrate concentration of the Maringa region (Parana State, Brazil) aiming at nitrate removal by coagulation/flocculation using a natural coagulant obtained from the seeds of the Moringa oleifera Lam. plant (MO) combined with an activated carbon filter. Groundwater samples were collected in Maringa City metropolitan area and characterized by physicochemical analyses. The results showed groundwater NO3- concentrations ranging from 0-60mg NO3- L-1. Thus, the nitrate variation in the water used in the coagulation/flocculation assays lay between 10-60mgL(-1) of NO3-. In these assays both aqueous and saline MO raw extracts were added (concentrations between 0.25-11gL(-1)). Coagulation/flocculation treatment with aqueous MO extract presents nitrate removal of 73.3%, and saline MO extract presents 85.4%. The source that presented the highest nitrate concentration along with the ideal MO concentration in the coagulation/flocculation process was used for the coagulation/flocculation process followed by activated carbon filtration. The treatment with MO combined with the filter met Brazilian, American, and international potability standards for nitrate and turbidity. The present study reveals the presence of nitrate in the groundwater of the area and also enables new procedures for treating this kind of water in small rural properties and needy communities.