The present study aims to investigate the influence of fly ash leachate (FL) on the hydraulic and mechanical behaviour of two Indian bentonites with discrete mineralogical and chemical compositions. The investigation revealed that both bentonites with different mineralogical and physical properties noticeably affected free swelling, Atterberg limits, swelling potential, swelling pressure, and hydraulic conductivity. However, a comparative assessment for both types of bentonites shows that swelling capability, liquid limit, cation exchange capacity, and the specific surface area experience a directly proportionate variation to the free swell (80% decline), liquid limit (74% decline), swelling potential (61% decline), and swelling pressure (59% decline) when permeated with FL. In addition, a rise in hydraulic conductivity (28 and 38 times rise at a void ratio of 1.1) was observed with leachate presence for both bentonites. The research findings would therefore prove constructive to engineers for deciding on bentonite types for liner application in landfills.