Membrane gas absorption or membrane contactor using polyvinylidene fluoride (PVDF) membrane has recently become an emerging application in industry. One of the commonly used absorbents in this application is sodium hydroxide (NaOH). This article presents the study of chemical and thermal stability of PVDF membrane in alkaline environments. Commercial PVDF flat sheet membranes were exposed to two types of alkaline solutions, which are NaOH and potassium hydroxide (KOH) at different concentrations, temperatures, and treatment times. The untreated and treated membranes were analyzed using FESEM (field emission scanning electron microscopy), DSC (differential scanning calorimetry), FTIR (Fourier transform infrared), pure water flux measurement, and tensile testing. The results demonstrated that PVDF membrane can be attacked and degraded upon exposure, even to a low concentration of 0.01 M NaOH solution, the concentration that commonly applied in membrane contactor applications, and cleaning. The findings from this study also suggested that PVDF membrane is more vulnerable to NaOH solution as compared to KOH solution.