Recent research on teacher burnout has advanced our understanding of its dimensions and contributing factors. However, the complexity and dynamics of the social working environments in schools has often been neglected in teacher burnout studies, and hence a valid and reliable context-sensitive instrument for studying teacher burnout in terms of social interaction in schools is needed. This study examined the development of the Socio-Contextual Teacher Burnout Inventory (STBI), its validity as well as reliability, among Finnish teachers (n = 2310). The validity and reliability of the items composing the STBI were determined based on the confirmatory factor analysis. The results showed that the correlated three-factor solution and second-order-factor solution fitted the data. More specifically, teacher exhaustion, cynicism towards the teacher community and inadequacy in the pupil-teacher relationship were found to be closely related but separate constructs. The results also supported the main hypothesis that teacher burnout can be examined in terms of interpersonal problems in an individual’s transactions with others in the workplace. Therefore the sources of teacher burnout may vary not only between schools but also between the social working contexts within a single school. The instrument introduced in this study is a potentially useful tool for exploring interpersonal teacher burnout.