Extreme temperature events, such as heat waves, are increasing in frequency, magnitude, and duration. These events are believed to contribute to pollinator decline. Critical thermal maxima (CTmax) is a key physiological trait for understanding an organism’s ecology and predicting its responses to changes in climate. In this study, we investigated whether different life stages with distinct thermoregulatory behaviors differ in their CTmax in the solitary bee Osmia bicornis, one of the most common and important pollinators in Central Europe. Additionally, we tested the influence of excessively high temperatures, heat waves, on the CTmax in Osmia bicornis. We found CTmax varied among life stages, with adults exhibiting higher CTmax than larvae. Both females and males of adult bees showed a negative correlation between CTmax and body mass. Interestingly, adult bees exposed to different heat waves during their larval stage did not exhibit significant shifts in CTmax. These results suggest that bees may have limited capacity to enhance heat tolerance in response to prior heat exposure.