Spirituality/religiosity is hypothesized to promote positive adjustment among adolescents. The goals of this study were to assess the unique and joint associations between two dimensions of spirituality/religiosity—institutional and personal—and a range of domains of psychosocial adjustment (intrapersonal well-being, quality of parent–child relationship, substance use, and academic orientation) and to evaluate the direction of effects in these associations. Participants included 803 predominately Canadian-born adolescents (53 % female) from Ontario, Canada, who completed a survey in grade 11 and grade 12. At the concurrent level, higher personal spirituality/religiosity consistently and uniquely predicted more positive adjustment in terms of well-being, parental relationship, and academic orientation. Higher institutional spirituality/religiosity uniquely and consistently predicted lower substance use, particularly when personal spirituality/religiosity also was high. With regard to the direction of effects (i.e., longitudinal associations), institutional spirituality/religiosity predicted lower future substance use. The results imply that the personal and institutional dimensions of spirituality/religiosity may be associated differentially with psychosocial adjustment, and it may be only in the domain of substance use that spirituality/religiosity predicts change in behavior over time.