The study was conducted in the main canal of Tendaho Reservoir, Awash Basin, Ethiopia, located at about 15 km South of Samara town and 580 km North-East of Addis Ababa. The objectives of the study were to generate valuable information on reproductive biology, feeding habits and some other biological aspects of C. gariepinus in the study area. Fish specimens were collected monthly from July 2012 to June 2013 using gillnets of various mesh sizes, and hook and lines. Immediately after capture, total length and total weight of each specimen were measured to the nearest 0.1 cm and 0.1 g, respectively. Then, each specimen was, dissected and the sex of the fish was determined by inspecting the gonads. Gonads of each specimen were removed and weighed to the nearest 0.01 g. The relationshir. between total length and total weight was curvilinear and represented as TW = 0.0031TL213, R2 = 0.9421, P<0.05. Fulton condition factor (mean ± SE) was O.75 ± 0.01 for females, 0.73 ± 0.01 for males. Clarias gariepinus feeds a variety of food items. However, insects, zooplankton and fish and fish remains were found to be the most important food of C. gariepinus in the canal. All size groups of the fish ingested the major food items during all sampling months of the study. However, the importance of insects and zooplankton tended to decrease whereas that of fish tended to increase with the increasing in TL of C. gariepinus. Thus, it appeared that C. gariepinus fed progressively more on fishes as it grew larger. High occurrence of empty stomachs was observed during the rainy season, which could be associated with breeding activity. The contribution of insects and zooplankton to the diet of C. gariepinus was relatively highest towards the end of the main rainy season, whereas the contribution of fishes and fish remains was relatively high during the rainy season of the upper part of the Awash River. The sex ratio, length at maturity and gonado somatic index were estimated. Ripe ovaries were preserved in 5% formalin to estimate fecundity. Stomach contents were preserved in 5% formaldehyde and analyzed in Afar Animal Health Regional Laboratory. Sex ratio was not significantly different from 1.' 1 except preponderance of females over males from samples taken in September and May. The 50% sexual maturity length (L50)was estimated to be 52 cm TL offemales and 57.3 cm TL of males. Gonado somatic index andfrequency of ripe gonads suggested that C. gariepinus in the main canal of Tendaho Reservoir breeds throughout the year with peak breeding season from July to September. The peak breeding season of C. gariepinus was synchronized with the rainy seasons in upper Awash and high temperature in the area. The estimated absolute fecundity was linearly related with TW and Gw, but curvilinear to TL and ranged from 5,523 to 1,093,828 with a mean of 205, 661. Generally the fecundity performance of C. gariepinus in the main canal of Tendaho Reservoir was high relatively to other Ethiopian water bodies. This may indicate better production, productivity and suitable environmental condition of the main canal of Tendaho Reservoir for the fish. Therefore, the fisheries management plan in the reservoir should consider the peak breeding season to be closed for fishers and maintain the natural foods for sustainable development of the fish resources.