In general, depending mostly on natural resources, the building sector is actively looking for sustainable substitutes for conventional cement to lower its environmental impact. The vi-ability of substituting Cashew Nutshell Ash (CNSA) partially for cement in M25 grade concrete is investigated in this work. By substituting the cashew nut shell ash for the different proportions (0, 5, 10, 15, and 20% by weight) of cement, this work investigates the mechanical, physical, and durability behaviour of concrete. After that, compressive strength, tensile strength, flexural strength, and resistance to acid attacks were investigated extensively experimentally. Furthermore, Scanning Electron Microscope (SEM) was used for the microstructural behaviour analysis. The results imply that substituting cement for 10% of CNSA has shown positive effects, so enhancing the sustainability and cost-effectiveness of concrete production without sacrificing strength and durability. This work shows the possibilities of CNSA as an environmentally-friendly additive for cement, so supporting more sustainable building techniques. © 2025 Elsevier B.V., All rights reserved.