Rainwater harvesting is a promising tool for augmenting surface water and groundwater supply. This study has made an attempt to prioritize the Noyyal basin, Tamil Nadu, using GIS based weighted overlay analysis. Rainwater harvesting potential zones were delineated using the maps corresponding to slopes, drainage density, lineament density, soil, landuse, geology, rainfall and geomorphology. Each thematic layer was reclassified and suitable weightages were assigned to these layers and also to the different classes of each layer based on their relative influence on rainwater harvesting potential. The potential zone score was computed by using weighted overlay analysis. Rainwater harvesting potential zones in the study area are classified based on rainwater harvesting potential score. A high runoff potential area was designated for approximately 16 percent of the watershed.