Objective: To test feasibility of yoga within a high school curriculum and evaluate preventive efficacy for psychosocial well-being. Methods: Grade 11 or 12 students (N = 51) who registered for physical education (PE) were cluster-randomized by class 2:1 yoga:PE-as-usual. A Kripalu-based yoga program of physical postures, breathing exercises, relaxation, and meditation was taught 2 to 3 times a week for 10 weeks. Self-report questionnaires were administered to students 1 week before and after. Primary outcome measures of psychosocial well-being were Profile of Mood States—Short Form and Positive and Negative Affect Schedule for Children. Additional measures of psychosocial well-being included Perceived Stress Scale and Inventory of Positive Psychological Attitudes. Secondary measures of self-regulatory skills included Resilience Scale, State Trait Anger Expression Inventory-2™, and Child Acceptance Mindfulness Measure. To assess feasibility, yoga students completed a program evaluation. Analyses of covariance were conducted between groups with baseline as the covariate. Results: Although PE-as-usual students showed decreases in primary outcomes, yoga students maintained or improved. Total mood disturbance improved in yoga students and worsened in controls (p = .015), as did Profile of Mood States-Short Form (POMS-SF) Tension-Anxiety subscale (p = .002). Although positive affect remained unchanged in both, negative affect significantly worsened in controls while improving in yoga students (p = .006). Secondary outcomes were not significant. Students rated yoga fairly high, despite moderate attendance. Conclusions: Implementation was feasible and students generally found it beneficial. Although not causal due to small, uneven sample size, this preliminary study suggests preventive benefits in psychosocial well-being from Kripalu yoga during high school PE. These results are consistent with previously published studies of yoga in school settings.