<p>Dewatering systems featuring dewatering drain holes represent one of the critical efforts toward maintaining the continuation of Grasberg mine activities. Geologically, the Grasberg mine complex is characterized by limestone dominance as well as the intersections of the northwest-southeast trending major faults and northeast-southwest trending major faults, resulting in fractured or jointed groundwater-bearing media that strongly influence the mine’s dewatering activities. Hydrogeologically, the groundwater system in the Grasberg mine area is characterized by groundwater flow in fractured media, with the flow tending to be segmented, making it difficult to determine suitable locations for dewatering drain holes. Suitable locations for dewatering drain holes need to be optimized to increase the success of the mine’s dewatering program. This paper intends to share the results of a study conducted at the Grasberg mine in terms of how to determine such suitable locations for dewatering drain holes using a spatial database. A fuzzy spatial decision support system was applied to help determine suitable locations for the drain holes based on fuzzy inference system. The parameters used to determine the suitable dewatering drain hole locations included rock quality designation, hydraulic conductivity, and the water flow rates from dewatering drain holes for the years 2006–2014. The fuzzy inference system was used to map the spatial input parameters to the spatial output parameter, which, in this case, is the suitable locations for dewatering drain holes. Analysis of such locations indicated that the most suitable areas for drain hole installation are mostly in the northwest, northeast, and southwest areas of the Grasberg mine.</p>