Evidence shows that those who practice Buddhism have positive mental health. Such research, however, is nearly non-existent in Vietnam, a country with a long Buddhist tradition. What is the relationship between non-attachment and mental health (stress, anxiety, and depression) in Buddhists, and what is the most influential variable that affects the non-attachment and mental health of Buddhists? The purposes of this study are (1) to examine the relationship between non-attachment in Buddhism and several mental health components (stress, anxiety and depression), and (2) to explore, within the demographic and religious variables, the most influential variable that affects the non-attachment and mental health of Buddhists. The participants were 472 Buddhists (427 laypersons, 45 monks; 339 women and 130 men) from four sanghas located around Vietnam. Data were collected from January to April of 2016. Each participant underwent a battery of measures comprised of the Non-attachment Scale, the Depression, Anxiety, and Stress Scale (DASS-42), and a demographic questionnaire. A negative correlation was found between non-attachment and negative mental health components (stress, anxiety, and depression) within the sample group. Three variables -frequency of practicing dharma, belief in dharma, and change of mind since practicing dharma -were correlated with non-attachment and mental health. Frequency of practicing dharma and change of mind since practicing dharma were the best predictors of non-attachment and positive mental health. Results showed that practicing non-attachment improves mental health. Practicing Buddhism is strongly related to religious commitment, which helps individuals strengthen their beliefs in Buddhism and non-attachment, where they are free of external pressures and, hence, happier.