Development of high-performance composites operating in harsh conditions is gaining tremendous attention due to the broad range of applications such as mass transport, defense, energy, manufacturing, electronics, healthcare, and so forth. Some of the current challenges include the development of lightweight composites suitable for high or low temperatures, high impacts, and corrosive or radiation environments. Among various nanomaterials, graphene-based materials have emerged as the most popular class of nanoadditive that can revolutionize every industry sector. Herein, we briefly discuss the properties of graphene as a potential additive for high-performance composites. The review focuses on the functional properties of graphene-based polymer nanocomposites in a range of harsh operational conditions, such as cryo-mechanical properties, ballistic impact resistance, thermal conductivity, deicing/anti-icing behavior, self-cleaning, sensing properties, and flame-retardant properties. Finally, we conclude with an outlook for the development of graphene-based polymer nanocomposites for harsh conditions by deliberating the major progress, challenges, and opportunities.