The rationalization of concrete mix components can yield several benefits, encompassing cost efficiency, enhanced performance, and diminished environmental impact. Cement, a primary binding material in concrete, faces challenges in meeting escalating demand due to rapid urbanization. Partial substitution of cement with alternative materials offers a solution. The selection of a suitable replacement material depends on specific requirements and cement conditions. The judicious use of replacement materials can enhance concrete's performance, durability, and workability while meeting strength criteria. Fly ash from thermal power plants is a widely utilized cement admixture, but its availability and environmental sustainability pose challenges. Eco-friendly alternatives, such as coconut shell ash (CSA) derived from coconut shell (CS), present viable options for partial cement replacement. This study employed CSA through a methodology involving CS combustion in a boiler at temperatures ranging from 300°C to 350°C. Ash collected from the boiler bottom, sieved through a 90-micron IS sieve, formed the basis for further investigation. The research focused on ordinary portland cement (OPC), coal ash (CA), and CSA. Chemical tests assessed parameters like loss on ignition (LOI), magnesium oxide (MgO), sulfuric anhydride (SO3), insoluble residue, percentage of lime (SiO2, Al2O3, and Fe2O3), chloride content, and Al2O3 to Fe2O3 ratio per IS CODE:4032-1985 for material composition. Results were cross-verified against IS CODE 269:2015 (OPC- 43 Grade). Physical tests, including fineness, soundness, initial and final setting and compressive strength, were performed to assess quality aspects. Partial replacement ratios of 0%, 5%, 10%, 15%, and 20% were determined. The chemical test results highlighted a high MgO content in Coconut Shell Ash (approximately 21.8%), exceeding IS 269:2015 standards. Physical tests indicated that MgO prolonged the cement setting time in OPC/Coconut Shell Ash mixes by up to 15%. Compressive strength measurements after 3, 7, and 28 days revealed a 14.42% increase in the average strength of portland cement concrete (PCC) compared to a 6.6% increase for OPC, underscoring the potential benefits of CSA, as a partial cement replacement.