Prior research has demonstrated that religiousness is associated with and potentially facilitative of self-regulation, though most of the research has been cross-sectional. The present longitudinal study examined dynamic relations between religiousness development and self-regulation formation from early adolescence into young adulthood. The sample included 500 U.S. adolescents and their parents. The data were restructured by adolescent age and analyzed from ages 11-22. The analyses involved latent curve models with structured residuals (LCM-SR). First, univariate latent growth curve models were estimated for religiousness, as well as adolescent-reports and parent-reports of adolescent behavioral self-regulation, cognitive self-regulation, and emotional self-regulation. Religiousness decreased over time while self-regulation increased (except for adolescent-report behavioral self-regulation, which followed a u-shape). Bivariate latent growth curve models pairing religiousness with each self-regulation variable found significant positive correlations between change in religiousness and change in adolescent-report cognitive and emotional self-regulation and parent-report emotional self-regulation. After adding in cross-lagged paths, relations between these slopes went away, but positive bidirectional cross-lagged associations in both directions were found between religiousness and adolescent-report cognitive self-regulation and parent-report emotional self-regulation. These results provide evidence for dynamic relations between religiousness and self-regulation across adolescence and into young adulthood. Further, the findings point to possible specificity based on the self-regulation dimension and whether data are adolescent-report or parent-report.