Mortar is yet the major construction material used in the growing Ethiopian construction industry. Mortar is used in the different building locations on the building segment such as; load-bearing and non-load-bearing building structures. This research is important for Preserving the limited natural resources of cement mortar constituents and effective utilization of materials like cement, aggregates, and water, are important in minimizing wastes and decreasing the costs of mortar. This research was considerable efforts are being undertaken to utilize Cow Dung Ash (CDA) wastes and Cow Dung Ash prepared by furnace at 800 oc in 2 hours as an alternative supplementary cementitious material to produce mortar and reduce cost of cement. The detailed experimental analysis is conducted to assess the study is investigated chemical composition of CDA and conduct different tests: workability; compressive strength; sulfate attack; water absorption; ultrasonic pulse velocity (UPV) and microstructure tests such Thermogravimetric Analysis (TGA), Differential thermal analysis (DTA) and Fourier Transform Infrared (FTIR)) are investigated in partially replacing Ordinary Portland Cement (OPC) with Cow Dung Ash. Different mortar cubes were cast with varying mixing proportions of CDA: 5%, 10%, 15% 20%,25%and 30% by weight Ordinary Portland Cement. Control mixes are made using regular Ordinary Portland Cement mortar mixes. All mortar cubes are cured in a laboratory setting and testing measures of 3, 7, 28, and 56 days are recorded. The results show that CDA replaced mortar shown as increasing of Cow Dung Ash; the decreasing compressive strength with minimum strength at CDA30 (15.07 Mpa) at 3rd day curing age and maximum compressive strength on CDA0 (40.79 Mpa) at 56th days of curing age, upv, sulfate attack resistance, and workability and increasing of water absorption than the control mixes. This study explains the use of Cow Dung Ash as a potential replacement for cementitious material. However, Cow Dung Ash replacement affects mechanical properties, the result showed the difference was insignificant up to 25% Cow Dung Ash replacement based on compressive strength. This type of research is very important for East Africa region for satisfying to booming construction industry.