Free-living vertebrates tend to respond to environmental challenges by increasing circulating glucocorticoid levels. Changes in glucocorticoids can modulate various aspects of physiology and behavior, which can have fitness benefits in the short term but may be detrimental to fitness if elevated levels are frequent, prolonged, or both. The transfer of glucocorticoids from females to offspring might also have fitness consequences, but there is less known about the potential effects of transgenerational glucocorticoid transfer. Our study examined corticosterone levels in female Red-eared Sliders (Trachemys scripta) during the nesting season because of the potential fitness consequences for both females and offspring. Whether caught in aquatic traps or caught during the nesting process, females had similar circulating corticosterone levels that were relatively low. However, when females were subjected to a restraint protocol, corticosterone rose. Therefore, corticosterone levels may be elevated during the nesting process, but the nesting process itself does not result in elevated corticosterone levels. Understanding how natural processes such as nesting influence corticosterone levels has important consequences for interpreting corticosterone levels as an index of fitness.