Global governments and industries are working to combat climate change caused by greenhouse gas emissions from cement production, which accounts for about 7% of global CO2 emissions. This research aims to reduce environmental contamination by using alternative materials in cement. Specifically, waste marble powder (WMP) and wheat straw ash (WSA) tested as substitutes in mortar production. Trial compressive strength tests identified a 1:2 ratio as optimal for combining WMP and WSA. Five mixtures designed: one control without replacements and four with 5%, 10%, 15%, and 20% cement replacement by weight, maintaining a constant w/c ratio of 0.53. A comprehensive experimental analysis evaluated the fresh (workability), hardened, and microstructural properties of the mortars. Mechanical properties (compressive strength) and durability (porosity, water absorption, and ultrasonic pulse velocity) investigated at 3, 7, 28, and 56 days of curing. Additionally, FTIR and SEM analyses conducted for the 0%, 10%, and 20% replacement mixtures at 56 days of curing age, while DTA and TGA properties examined at 7 and 56 days of curing age. The result shows that adding waste marble powder and wheat straw ash to mortar decreased workability but increased compressive strength, with the best results at 10% replacement. The results showed that incorporating waste marble powder and wheat straw ash improved the mortar's durability. SEM analysis revealed a dense microstructure in the WMPSA 10 mix, while DTA and TGA results indicated greater thermal stability compared to the control mortar. The correlation of mortar properties shows a positive relationship between compressive strength with UPV and porosity with water absorption, while UPV has a negative correlation with porosity. It is recommended to replace up to 15% of the cement on mortar with waste marble powder and wheat straw ash. Keywords: Waste Marble Powder, Wheat Straw Ash, Cement Mortar, Durability, Microstructure