Production of cement involves the emission of large amounts of carbon dioxide into the atmosphere, a significant contributor to global warming, and also Mining and extraction of natural sand contribute to deepening river beds leading to riverbank erosion and air and water pollution. On the other hand, a high volume of industrial production has generated a significant amount of waste materials which have a huge impact on the environment. In this regard, the speedy growth of the marble industry introduces concerns on the environment through producing a waste which is very polluting due to its alkaline nature. Similarly, more than twelve thousand tons of fly ash generated in a year from Reppie waste to energy plant in Addis Ababa deposited in landfilling which impose serious health threats to the environs. This study aims to investigate the property of mortal containing waste marble powder and fly ash as cement and river sand substitution. To this end, 12 series of mixes with a total of 540 mortar specimens were prepared. Waste marble powder and fly ash replaced cement at 10%, 15%, 20%, 25%, 30%, 35% & 40% and waste marble replaced river sand at 10%, 20%, 30% & 40% by weight, in all mixtures, water to cement and sand to cement ratio was kept constant at 0.5 and 1:2.75 respectively. The fresh properties of the mortar mixtures were determined by the flow table, Tests on hardened mortar include compressive, flexural, split tensile strength, water absorption, and to ensure its ability against aggressive environments, the durability properties such as water permeability & sulfate resistance was investigated. Also, Thermogravimetric Analysis, Differential Thermal Analysis and Fourier transform infrared spectroscopy were used to analyze microstructural behavior of the samples. The result indicated that adding Waste marble with lower percentage (i.e 10-20%) improves workability and had better mechanical property than the control mixes, further addition results reduction in mechanical strength, mortar specimens with Waste marble were found to have better sulfate resistance than the control mixes. And the control mix has good thermal stability than samples with Waste marble powder. The finding of this study will help in utilizing alternative sustainable construction materials to reduce environmental impacts.