As the environment changes, populations can respond by adapting via evolutionary change. If the rate or magnitude of environmental change is too great for evolution to keep pace, then populations face the risk of extinction. While the majority of species that have ever lived have gone extinct, the wealth of extant biodiversity on Earth proves that many lineages have successfully survived and diversified in response to the extensive environmental challenges thrown at them since life began. This chapter evaluates the important role phenotypic plasticity—the ability of a single genotype to produce different phenotypes in response to environmental variation—may play in ‘buying time’ for populations to persist and potentially then evolve when confronted with rapidly changing or novel environments. The history of the buying time concept is reviewed as well as the theoretical predictions regarding when phenotypic plasticity will or will not be able to buffer populations in changing and novel environments. The empirical evidence for plasticity buying time is synthesized, and a framework is developed for future tests of buying time focusing on organismal responses to novel urban environments as an example Finally, this chapter discusses the open questions and future directions for further research on buying time.