The hydrolytic degradation of PLA film and PLA film modified with multi-functional epoxy-based chain extender was measured in water at elevated temperatures from 40 to 95 °C. A phenomenological model was used to describe the hydrolytic degradation process of the films by considering the decreasing of molecular weight and the chain scission inducing crystallization as a function of time. A deconvolution technique was used to determine the subpopulation of the asymmetrical molecular weight distribution (MWD) curves. The main peak fitting representing the majority of chain population from the MWDs was used to estimate the rate of degradation of modified PLA with chain extender compared with neat PLA. The rates of hydrolysis of PLA significantly increase as temperature increased. With the presence of chain extender, the rate of hydrolysis decreased by 48 to 66 % within the experimental temperature range. The predictions can be used to estimate the lifetime of PLA and modified PLA in water between the tested temperatures.