Energy crisis has emerged as a serious issue in developing countries. Ethiopia facing similar crisis that has resulted infrequent power failures and load shedding throughout the country for past several years. Identification and utilization of new renewable energy resources site is of crucial importance to reduce the energy shortage and fossil fuel dependency throughout the country. The objective of this study is to assess micro to small hydroelectric power potential site on Gedeb River, Abbay basin Ethiopia. Data used in this study include digital elevation model (DEM), stream flow and areal rainfall data. Geographical information system (GIS) tool was used for processing and extraction of contour lines, drainage order, slope map, stream map generation and inverse distance weight areal rainfall interpolation. By overlapping drainage order map, slope map and contour lines map using GIS, Ten potential sites were identified in the study area. To select hydropower potential sites, extraction and selection of feasible stream reach along the river flow path profile is done.4th and higher order streams having ≥2% slope gradient within 500 meter maximum stream length were the main criteria to identify feasible stream reach and to select each hydropower site. From all potential sites, site1 and site10 have maximum and minimum potential capacity; 4935.8KW and 39.4KW respectively. The maximum installed capacity from 30% FDC flow values and the minimum firm power from 90% FDC flow values for all sites were estimated as 21150.1KW and 745.9 KW respectively. Analytical hierarchy process was chosen in combination of geographic information system (GIS) as the method of multi-criteria decision making on best prioritize hydropower site selection. Discharge, head, power, road accessibility, site distance from nearby town and geological layer resistance were considered as a criteria in this study and according to the suitability analysis result, site 4 and site 5 were selected as 1st and 2nd ranks for best suitable sites respectively and site 10 is considered as low suitable from all sites. From ten potential sites in the study area According to Ethiopian classification based on their installation capacity, five sites are small scales, two sites are mini scales and three sites are micro scales.