Concrete is a versatile and widely used construction material that has been popular for a long period of time. Its dominant position can be attributed to the ongoing processes of industrialization and urbanization taking place worldwide. Cement, its primary component, is consumed in substantial quantities annually, but its manufacture entails significant energy consumption, resulting in substantial CO2 emissions and high production costs. To overcome these problems we can use agricultural and industrial wastes as a partial replacement of cement for concrete production. Additionally, the environmental impact of wastes is also reduced. The aim of the this study was to investigate the effect of partial replacement of cement with rice husk ash (RHA) and waste marble powder (WMP) for cement mortar production. RHA and WMP partially replaced OPC 0% to 30% by weight with 5% interval. The fresh (consistency, setting time and workability), mechanical (compressive strength and ultrasonic pulse velocity (UPV)), durability (sulfate attack, water absorption and porosity), microstructure (thermogravimetric analysis (TGA), deferential thermal analysis (DTA), fourier transformation infrared (FT-IR)) were studied. In addition, all physical properties fine aggregate, X-ray florescence (XRF), BET specific surface area and specific gravity of RHA and WMP were also tested. The results indicated at 28 days of curing that the compressive strength improved by 20.65% at a 20% replacement level, promoting homogeneity through a packing effect and the pozzolanic reaction that forms additional calcium silicate hydrate. Water absorption also obtained as 8.3 and 6.34 in 0% and 20% replacement at 28 days of curing respectively. The improved uniformity resulted in reduced porosity and water absorption, leading to enhanced resistance against sulfate attack. However, the workability of the mortar decreased with increasing replacement percentage, particularly the replaced materials exhibited higher fineness (i.e., higher specific surface area). Additionally, the mass loss was minimized with 13% at a 20% cement replacement level. The overall properties of cement mortar containing RHA and WMP was improved up to 20% of the partial replacement of cement. Finally, the recommendation is to utilize agricultural and industrial wastes as a partial replacement of cement in the production of mortar/concrete should be encouraged. Key Terms Rice Husk Ash, Waste Marble Powder, Fresh properties, Mechanical Properties, Durability, Microstructure