The spatial and temporal variations of physical, chemical and biological water quality parameters were used to assess the quality of drinking water in Gondar town and evaluate the performance of its treatment plant. The town gets its water supply from Angereb reservoir, Kolladeba boreholes, and from four springs situated around the town. Water samples were collected on a monthly basis from all the sources and from 32 tap users at nine pressure zones in the distribution systems. The collected samples examined in a laboratory for physiochemical and bacteriological analyses. Thirty-five sampling sites were chosen along the watercourse. To characterize the water quality, was examined using 14 water quality parameters:- water temperature, electrical conductivity, turbidity, PH, total dissolved solids, nitrate(NO3-), nitrite(NO2), phosphate(PO43-), ammonia(NH3) iron (Fe), dissolved oxygen, free residual chlorine, total coli form and fecal coli form. All the water quality parameters at all water sources significantly vary (p<0.05). Most of the water quality parameters at distribution systems significantly vary (p<0.05) at the tap customers along the pipelines in the distribution systems except PH. The water quality also showed higher values of the examined parameters in the rainy season than the dry season in the year 2017/18. All water quality parameters at all water sources were within the WHO guideline except the temperature, phosphate, total coliform, fecal coliform, and free residual chlorine parameters. All parameters showed increment in concentration from water sources to distribution system both in wet and dry season. Therefore, it can be concluded that along distribution system, the drinking water is prone to contamination and the water quality decline along distribution system. Comparison of the results with WHO and the Ethiopian drinking water quality standards indicated that the raw water from Angereb is of poor quality, while the treated water is satisfactory. Therefore, the performance of the Angereb treatment plant was in good condition with turbidity removal efficiency of 99.66%.