The advancement of polymer nano-composites has been motivated by the need for materials with a specific combination of mechanical properties beyond those achieved from only one material. Integration of reinforcement into polymers at nanoscale can provide a significant increase in numerous physical and mechanical properties of polymer nano-composites. However, in applications where contact with chemically reactive liquid media is unavoidable, the mechanical properties of polymer nano-composites suffer degradation and environmental stress cracking (ESC) which is a commonly observed phenomenon. Moderate and severe aggressive liquid can cause ESC while non aggressive liquid are also capable of lowering the mechanical properties of polymer nano-composites by acting as plasticizer. To date, only few studies are reported discussing the ability of nano-fillers to resist ESC in polymer nano-composites when exposed to chemically reactive liquid media. In this review, various factors responsible for ESC in polymer nano-composites and their remedies are studied.