Low-elevation species can migrate toward higher elevations to survive in a warming world. However, animals' responses to hypoxia when migrating to high elevations have rarely been addressed. To identify the response of low-elevation lizards to high-elevation hypoxia, we collected field body temperatures (Tfb ) and operative temperatures (Te ) of lizards (Eremias argus) from a low-elevation population (1036 m) and a high-elevation population (2036 m), and then determined adult thermal physiology, embryonic development, and hatchling phenotypes after acclimating low-elevation lizards and incubating their eggs in conditions mimicking the low-elevation oxygen condition (18.5% O2 ) and high-elevation oxygen (hypoxic) condition (16.5% O2 ). Our study revealed that Tfb and Te were higher for the low-elevation population compared to the high-elevation population. We also found adults from low elevation acclimated to hypoxia preferred lower body temperatures, but did not show changes in locomotor performance or growth. In addition, hypoxia did not affect embryonic development (hatching time and success) or hatchling phenotypes (body size and locomotor performance). These results suggest that adult lizards from low elevations can respond to hypoxia-induced stress when migrating to high elevations by behaviorally thermoregulating to lower body temperatures in order to sustain normal functions. Similarly, low-elevation embryos can develop normally (with unchanged hatching success and offspring phenotypes) under the high-elevation hypoxic condition. This study highlights that low-elevation populations of a species that inhabits a range of elevations can buffer the impact of high-elevation hypoxic conditions to some degree and thus attain similar fitness to the source population.