An organism's thermal limits provide valuable insights into species distributions and potential climate change impacts. The critical thermal maximum (CT_max) in particular has been widely used for among-species analyses of thermal tolerances. However, CT_max measurements can depend on important context-dependencies, including acclimation temperature and experimental procedure. We investigated acclimation effects on CT_max in two amphibian species commonly used as laboratory models, Ambystoma mexicanum (Axolotls) and Xenopus laevis (African Clawed Frogs), using the standard dynamic method. Both species exhibited an increased CT_max following acclimation to a warm temperature (24°C) relative to cold acclimation (8°C). We also found that warm-temperature acclimation resulted in significant mass losses in both species, possibly reflecting metabolic costs of living at higher temperatures. Our CT_max measurements for A. mexicanum were consistent with CT_max measurements for closely related salamander species, but CT_max measurements for cold-acclimated X. laevis were inconsistent with a prior study of this species. This might have been because of the earlier study employing a less common curve-fitting method to estimate CT_max. These results highlight the importance of accounting for recent acclimation temperatures when estimating amphibian thermal limits and provide further support for the generalization that most amphibian species exhibit increased CT_max following warm-temperature acclimation.