I observed multiple adult California red-legged frog (Rana draytonii) approximately 4 feet inside an abandoned mine shaft located in the foothills above Cambria, San Luis Obispo County, California. This species, listed as threatened under the U.S. Endangered Species Act, is typically found in freshwater habitats with dense riparian vegetation. The shaft’s interior—cool, humid, and shaded with approximately 2 to 3 feet of standing water—provided suitable microhabitat conditions despite its anthropogenic origin. This incidental finding suggests that R. draytonii may utilize non-traditional structures such as mine shafts as refugia during periods of environmental stress, such as drought or extreme heat. The observation underscores the potential conservation value of artificial underground habitats in fragmented or degraded landscapes. While anecdotal, this record contributes to a broader understanding of habitat plasticity in R. draytonii and highlights the importance of including uncommon structures in habitat assessments. Further study is recommended to evaluate the frequency and function of mine shaft use in the species’ range, particularly in areas lacking traditional aquatic refuges.