Past research provided strong evidence that positive family-school partnerships were not only beneficial for students' school success, but they also helped to promote parental involvement in schooling. However, relatively little is known about teachers' reasons for becoming engaged in family-school partnerships and the benefits of their engagement. In fact, the role of teachers in family-school partnerships requires prosocial actions (e.g., helping, sharing, feeling empathy). As guided by self-determination theory, previous studies suggest that prosocial-oriented persons tend to take prosocial actions and these actions tend to promote a social connection, thereby promoting well-being. To the best of our knowledge, this assumption has not been applied to research on family-school partnerships yet. The aim of this study was to examine whether teachers' prosociality would be associated with their well-being at work (i.e., job satisfaction, work-related self-esteem) and whether this connection would be mediated by teacher engagement in family-school partnerships. Using the framework of the Vodafone Foundation Germany, we focused on two important aspects of teacher engagement: effective communication and educational cooperation. A total of 190 teachers (72% females; mean age: 44.78 years) participated in an online-survey. In line with SDT, teachers' prosociality was associated with greater well-being at work even after controlling for teachers' background (age, gender, experience, school track). As expected, this connection was partially mediated by teacher engagement in family-school partnerships. The results and implications of the present study are discussed.