Research suggests that lay persons’ conceptualizations of religion and spirituality may differ from how researchers operationalize these terms. Also, emerging evidence has identified that one’s cohort may influence how one defines religion compared to spirituality. More research is needed to explore how cohort differences influence participant responses on measures of these terms. Specifically, this study employed a mixed-methods design to compare religiousness and spirituality conceptualizations across the lifespan. A community-dwelling sample with equal representation from four age cohorts were recruited for participation in this study through Amazon’s Mechanical Turk platform. Participants completed a battery of quantitative measures and provided typed open-ended responses to qualitative items. The two forms of data were analyzed separately; then, the results were merged to interpret the points of convergence and divergence. The results of this study suggest that the quantitative measures included in the study adequately represent the differences per cohort on defining religiousness compared to spirituality. Additional analyses of the qualitative data may further explain those differences. Thus, the results of this study have the potential to guide researchers in revising quantitative measures of these terms to account for cohort differences. Lastly, the study suggests the importance of respecting clients’ conceptualizations of these terms and the potential use of these terms by mental health professionals’ when clients receiving services express interest in discussing their religious and spiritual beliefs.