BACKGROUND: The stresses of modern work life necessitate effective coping strategies that are accessible and affordable to the general public. Yoga has been found to reduce stress in clinical samples, but studies are needed to examine standard gym yoga classes among functional individuals. OBJECTIVES: This study investigated the effects of 8- and 16-week gym yoga on stress and psychological health. DESIGN AND METHOD: Ninety individuals reporting moderate-to-high stress were randomly assigned to 16 consecutive weeks of yoga, or to a waitlist crossover group who did not practice yoga for 8 weeks then practiced yoga for 8 weeks. Stress and psychological health variables were assessed at baseline, 8 weeks, and 16 weeks. RESULTS: Significant reductions in stress and all psychological health measures were found within the Yoga group over 16 weeks. When compared to the control group, yoga practitioners showed significant decreases in stress, anxiety, and general psychological health, and significant increases in well-being. The group who did not practice yoga showed significant decreases in stress, anxiety, depression, and insomnia after they crossed over and practiced yoga for 8 weeks. CONCLUSIONS: Gym yoga appears to be effective for stress amelioration and promotion of psychological health among workers experiencing stress.