The increasing challenge of managing residual ash from municipal solid waste incineration (MSWI) in developing countries necessitates innovative solutions for sustainable waste management. This study aims to explore the feasibility of using MSWI ash as an alternative material for landfill liners, thereby reducing environmental impacts. This study presents a detailed shear strength characterization of both fresh and aged MSWI ash (fly ash and bottom ash) collected from waste to energy (WTE) plant. Unconfined compressive strength (UCS) and direct shear test (DST) are employed to evaluate the shear strength of MSWI ash, which is crucial for its effective use in geotechnical engineering. The methodology involves systematic sampling and testing to assess the cohesion and internal friction angle of the ash, which are key parameters in liner design. The results reveal that MSWI ash possesses adequate shear strength, with cohesion and friction angles comparable to conventional liner materials. This indicates its potential effectiveness in providing structural stability and integrity in landfill applications. By incorporating MSWI ash, the volume of ash residue is significantly reduced, offering an eco-friendly and economically viable solution.