Abstract: The beneficial acclimation hypothesis (BAH) claims that all acclimation changes would enhance the physiological performance or fitness of individual organisms. In other words, animals acclimated to a particular environmental condition would enhance performance or functional fitness at that condition in comparison with animals acclimated to other environmental conditions. Although intuitively appealing, several studies challenged the generality of this hypothesis. Here, we expounded the definition and connotation of BAH, and summarized the main positive supporting evidence as well as the negative evidence in BAH verification. Furthermore, we proposed the prospects of future theoretical and experimental research on BAH verification.