This study analyzed the relationship between mindfulness and variables considered relevant for teacher–student interactions: teacher burnout, general stress, anxiety, depression, and quality of life. We hypothesized that mindfulness would relate negatively with mental health variables and positively with quality of life. We also explored which specific aspects of mindfulness would predict burnout, depression, anxiety, stress, and quality of life. Given the results of regression analyses, mediation models were performed to explore the mechanisms through which different facets of mindfulness affect quality of life. As predicted, the correlation analysis showed that mindfulness and its dimensions were positively associated with the quality of life of the teachers and burnout dimension of personal fulfillment and negatively associated with anxiety, depression, and stress (considering FFMQ total score and most of its dimensions). Consistently, regression analysis showed that the overall level of mindfulness, after controlling for the grade level at which the teacher works, showed significant associations with the level of personal fulfillment, depression, anxiety, stress, and quality of life. The results of the mediation analyses showed that the ability not to judge ourselves was associated with fewer symptoms of depression and stress and, through these pathways, positively affected quality of life. On the other hand, the ability not to react favored quality of life by reducing anxiety and stress. Finally, acting with awareness was the only facet of mindfulness that favored quality of life, affecting one of the dimensions of burnout.