BACKGROUND Reducing stress in the workplace improves mental health. Teaching is of social importance, but it may receive inadequate recognition and rewards. The present study compared mental well-being and state anxiety in primary school teachers who practiced 15 days of yoga in a residential setting with those who continued their usual routine. MATERIAL AND METHODS We enrolled 236 primary school teachers to participate in the study. We assigned 118 primary school teachers (group mean ±S.D., age 41.5±6.0 years, 74 females) to the experimental group; they underwent 15 days of yoga training for 6 hours/day) in a residential yoga center. The non-yoga control group (group mean ±S.D., age 42.3±6.0 years, 79 females) consisted of 118 teachers who continued with their normal teaching routine. RESULTS After 15 days in the residential yoga program, there was an increase in overall mental well-being (p<.001) and lower state anxiety (p<.01) (repeated-measures ANOVA, followed by post hoc multiple comparison tests). At baseline, the non-yoga control group had higher levels of state anxiety, presumably related to their remaining in the workplace. CONCLUSIONS The study was a 15-day, comparative, controlled trial. The results show that after 15 days of participation in the residential yoga program, primary school teachers increased all aspects of mental well-being and had reduced state anxiety.