Lake Tana water quality and biodiversity have been declined from year to year associated with point and non-point source contaminant from agriculture intensification, industrialization and urban pollution. Untreated discharge of urban, industrial and agricultural wastewater has impacted negatively on the water quality of Lake Tana. Plenty of studies have been conducted on assessment of pollution in Lake Tana but the effect of seasonal and spatial variations is still limited. Therefore, this study was intended to assess the Spatio-temporal variations of physicochemical parameters of Lake Tana at the periphery of Bahir Dar City. Three sampling stations were considered. Samples were taken at horizontal distances of 10m interval over a distance of 30m starting from the shore downstream to the main body of the lake, the place where the surface runoff was released. Similarly, 24 sampling points were taken at vertical distances of 0.5m, and 1.0m from water surface using a Van Dorn water sampler in all three stations. Primary data was collected by measuring devices to supplement the GPS accuracy on day times where the reception was not very good. Data collection was conducted when the lake was quiet. The result showed that water quality parameters like EC, TDS decrease from shore reference point to the main body along horizontally distance, while turbidity increases in the horizontal distance. The average BOD5 and PO43- significantly (p<0.05) differ in each station between dry and wet season. Overall, some of the physicochemical parameters, for instance, DO, TUR, PO43- and pH values were above WHO recommended limits. In conclusion, the physicochemical parameters of the water were varied in space and season in the periphery of the lake shore near to Bahir Dar City. This result is an indication of pollutions in Lake Tana. The study also recommended further research should be carried out by including all seasons of the year and wide horizontal and vertical sampling area to observe the detail Spatio-temporal variations of the physico-chemical parameters.