Given the well-established link between control beliefs and well-being, researchers have turned their attention to characterizing mechanisms that help foster this relationship across the second half of life. Cross-sectional, empirical work has identified a mediating relationship among religiosity and spirituality (R/S), control beliefs, and subjective well-being, such that individuals with higher R/S show higher subjective well-being that is mediated by between-person differences in perceived control. Empirical tests of between-person differences, however, may not represent within-person associations. As such, the present study utilized longitudinal data from the Notre Dame Study of Health & Well-being (NDHWB; N = 1,017) to examine concurrent, within-person associations among three R/S dimensions (i.e., religious coping, religious practices, and spirituality), control beliefs, and subjective well-being. Results from our Bayesian multilevel mediation analyses showed significant within-person associations among these constructs, suggesting potential bidirectionality and circularity in these processes. Cross-sectional age differences and time significantly moderated these associations. In terms of age differences, younger, compared to older, individuals showed stronger positive associations among religious coping and spirituality, control beliefs, and subjective well-being and more negative associations among religious practices, control beliefs, and subjective well-being. Contrarily, the effect of time implied that the relationships among religious coping and spirituality, control beliefs, and subjective well-being became more positive across time. Given this disjunction and that the moderating effect of cross-sectional age by time was not significant, cross-sectional age differences in these relationships likely reflect generational differences in the associations among R/S, control beliefs, and subjective well-being. (PsycInfo Database Record (c) 2022 APA, all rights reserved).