Clays have long been used in waste-confinement processes. However, there are not sufficient data in the literature presenting their sustainability under the effect of leachate water. As a case study, Ankara clay was chosen due to its suggested utilization as a landfill liner by previous researchers. Its sustainability under the effect of local leachate water, however, was left in question by earlier studies. In order to determine long-term effects of leachate water, samples were taken at three locations: Golbasi, Middle East Technical University, and Cigdem District. The disturbed samples were compacted with leachate water at optimum water content and cured for 1 and 4 months. The compressibility of the compacted Ankara clay was determined to be low, and curing with leachate water did not cause significant changes in the coefficient of hydraulic conductivity. In all locations, cohesion and internal frictional angle showed a decreasing trend after curing with leachate water. Also, cured samples showed lower Methylene Blue Value and Cation Exchange Capacity than natural samples. In addition, the mass of loss after freezing-thawing cycles for cured samples was higher than natural clay but lower than distilled water-compacted samples. The highest measured pH values were obtained from leachate-cured samples. Ankara clay meets the requirements of the Republic of Turkey Ministry of Environment and Forestry and the U.S. Environmental Protection Agency. The properties of the clay do not change significantly enough to outrange the requirements under the effect of leachate water. It has, however, a higher pH and mass of loss after freezing and thawing cycles than suggested values for clay liners presented in previous studies.