Soil fertility depletion due to soil erosion and nutrient leaching caused by heavy and continuous rainfall is one of the major causes for declining of soil productivity and crop yields in Masha district of south-western Ethiopia. Soil Hence, a field experiment was conducted in Belg and Meher seasons at Abelo area, Masha district, south-western Ethiopia, to determine the effect of combined application of cattle manure (CM) with inorganic nitrogen (N) and phosphorus (P) on potato tuber yield, and selected soil physico-chemical characteristics. The treatments comprised of combinations of three rates (2.5,5, 7.5 t ha-1) of CM with 25%, 50% and 75% of recommended rates of mineral NP, respectively. In addition, 100% recommended rate of mineral NP (165 kg N ha-1 and 137 kg P2O5 ha-1) and zero rates were used for comparison. The experiment was laid out in a randomized complete block design with three replications. The results revealed that applying 7.5 t ha-1 CM combined with 75% mineral NP gave significantly highest potato total tuber yield of (40 and 34 t ha-1), the same rate increased tuber yield by 55.9% and 43.45% in Belg and by 51.19%, and 36.64% in Meher over the control and the application of 100% recommended rate of NP fertilizers, respectivelysoil pH (5.15 and 4.94), Organic carbon (21.1and 12.7 g kg-1 ), total N (1.71 and 1.51 g kg-1), available P (7.55 and 6.27 mg kg-1), CEC (22.04 and 23.96 cmol (+) kg-1 ), exchangeable Ca+2 (8.36 and 8.28 cmol (+) kg-1), exchangeable Mg+2 (3.14 and 2.06 cmol (+) kg-1), total porosity (51.1 and 54.97%) more over the treatment decreases exchangble acidity (2.32 and 2.08 cmol+kg-1) and exchangble aluminum (1.46 and 1.41 cmol(+) kg-1), bulk density (1.07and 1.30g cm-3)  in Belg and Meher seasons, respectively. Therefore, it can be concluded that the use of combined application of 7.5 t of ha-1 CM together with 75% of recommended rates of inorganic N (123.75 kg N ha-1) and P (103.05 kg P2O5 ha-1). can significantly increase potato tuber yield and improve the soil properties and reduces soil acidity. Keywords: Cattle manure,physico-chemical properties, nitrogen, phosphorus, tuber yield.