An expanding body of literature has demonstrated that global climate change continues to adversely affect many populations, species, and ecosystems. However, life-history theory also predicts possible benefits from longer growing seasons and less severe winters, particularly for ectotherms. To test the idea that climate change will have benefits as well as costs, I studied the impacts of growing-season length on growth and overwintering conditions on survival time using side-blotched lizards (Uta stansburiana). Experiments in replicate field enclosures revealed that fall growing-season length has a direct effect on overwintering body size. Laboratory experiments revealed that both size and overwintering temperature have direct effects on winter survival time. Larger lizards are more likely to survive longer regardless of winter temperature. Furthermore, animals in colder (but still mild) winter microenvironments are more likely to survive longer than those in warmer winter environments. These results indicate that warmer winters caused by global climate change have the potential to negatively affect ectotherm populations. However, longer growing seasons may offset losses by allowing additional growth and energy storage. Thus, environmental alterations associated with climate change may be simultaneously beneficial and detrimental, and the long-term persistence of certain organisms may depend on the relative strength of their effects.