Objective/Methods: This research evaluates the effectiveness of a psychosocial wellness seminar for first-year college students, from 2009 to 2011, using an 8-month prospective quasi-experimental design. Participants/Results: Compared with controls ("n" = 22) involved in an alternative seminar, intervention participants ("n" = 29) showed no differences at baseline, but reported significantly greater perceived improvements over the course of the intervention, in psychosocial adjustment and stress management. Furthermore, specific aspects of intervention engagement (attendance and student-rated skills practice, but not didactic mastery or facilitator-rated skills practice) differentially predicted beneficial outcomes: (1) psychosocial adjustment (increases in psychosocial well-being, decreases in psychological distress), after adjusting for baseline levels of these outcomes; (2) college-related stress management (lower college-related stress, greater adaptation to college); and (3) perceived improvements in psychosocial adjustment and stress management. Conclusions: This research indicates promising avenues for programmatic efforts to promote psychosocial adjustment and stress management in college students, during this critical developmental juncture. (Contains 5 tables.)