Barriers/liners are one of the essential components of an engineered landfill design. These barriers avoid the percolation of the fluid that carries contaminants through the waste. Landfills operated without any liner cause severe contamination of the groundwater and also soil. The contaminated soil thereby loses its original properties leading to damages in the substructures. Hence, landfill liners are used to avoid geoenvironmental pollution. The performance of a liner material depends on the material properties such as low hydraulic conductivity, higher cation exchange capacity, and higher retention capacity. Neo materials such as fly ash, blast furnace slag, red mud, and kiln ash are being used as replacements for conventional materials to serve the purpose of liners. This study focused on the performance of fly ash under the influence of landfill leachate of various concentrations and evaluating its suitability, as a landfill liner. The experimental plan includes daily monitoring of permeability, pH, electrical conductivity, total dissolved solids, and concentration of Nitrates and Phosphates for virgin and leachate-contaminated fly ash. The experimental results reported that pH of fly ash was neutralized over time. Electric conductivity and total dissolved solids were reduced. Additionally, the hydraulic conductivity was found to be on the order of 10−10 m/s after a period of 16 days. These findings suggest that fly ash effectively neutralizes and reduces total dissolved solids. Moreover, the significant reduction in hydraulic conductivity over an extended interaction period further supports the potential fly ash as a suitable liner material.