Recent changes to the U.S. Preventive Services Task Force guidelines for breast cancer screening have contributed to increased patient uncertainty regarding the timing and appropriateness of screening behaviors. To gain insight into the lay epistemology of women regarding breast cancer screening practices, we conducted in-depth, face-to-face interviews with 24 adult women living in a medically underserved Appalachian region. We found that women were unaware of breast cancer screening guidelines (i.e., start age, frequency, stop age). Qualitative analysis revealed two lay epistemological narratives establishing (a) uncertain knowledge and ambiguity about breast cancer screening guidelines but certain knowledge of other women’s experiences with breast cancer diagnoses, and (b) feelings of knowing one’s own body best and seeing the value in “overscreening” to save even one life. Our findings have theoretical and practical implications for scholars and practitioners seeking to improve knowledge or behavior regarding adherence to breast cancer screening recommendations.