This study investigates the optimization of concrete mechanical properties by incorporating fly ash as a partial cement replacement and bottom ash as a substitute for fine aggregates. Utilizing a Design of Experiments methodology, the research systematically explored the effects of varying fly ash and bottom ash content on compressive, flexural, and tensile strengths. Concrete mixes with different replacement levels were prepared and tested after a 28-day curing period. Results indicated that while replacing cement and fine aggregates with 30% fly ash and 10% bottom ash maximized compressive strength, potentially due to fly ash's pozzolanic activity, higher replacement percentages led to a decline in compressive strength, possibly due to disruptions in particle packing and bond formation. Interestingly, the optimal mix for flexural strength was found to be 20% fly ash and 0% bottom ash. An unexpected outcome was observed for tensile strength, where a mix of 30% fly ash and 50% bottom ash exhibited superior performance. This unusual result requires further investigation to understand the underlying mechanisms and long-term implications. This study highlights the potential of utilizing industrial waste materials like fly ash and bottom ash to enhance concrete properties, contributing to sustainable construction practices while mitigating environmental impact. Further research is recommended to explore the durability and long-term behavior of these optimized concrete mixes.