<p>Concrete is one of the most commonly utilized in construction projects because of the rapid progress in urbanization and industrialization. The scarcity of natural resources and ongoing environmental degradation have propelled to explore alternative or supplementary materials for cement in concrete manufacturing. Cassava Peel Ash (CPA) is an agricultural byproduct that demonstrates strong potential as a supplementary for cement in concrete manufacturing. The aim of this study is to develop a High-strength Concrete (HSC) by partially replacing cement with CPA, an underutilized agricultural waste and enhancing its performance using Nano Silica (NS). Although CPA shows potential as a supplementary cementitious material, its use often results in reduced early strength. To address this limitation, this study investigates the combined effect of CPA (5, 10, 15, 20 and 25%) and NS (1, 2 and 3%) on the workability and mechanical properties of concrete. The developed concrete mixes are tested for slump, compressive strength, modulus of elasticity, split tensile strength and flexural strength at 7, 14 and 28 curing days. It was found that the inclusion of 5% CPA with 3%NS (C5N3) mix achieved the compressive strength of 70. 5N/mm² at 28 curing days. The results showed that the C5N3 mix achieved 20.8% and 27.2% and higher split tensile strength and flexural strength than the control concrete. The enhanced performance is due to the combined action of CPA and NS, which promoted pozzolanic reactions and developed a refined microstructure with increased C–S–H formation. It can be concluded that a C5N3 mix containing 5% CPA with 3% NS was found to be optimum for high-strength concrete applications.</p>