Many school systems face recurring shortages of qualified teachers. Research suggests that improving teachers' working environment is one way of improving teachers' job satisfaction and retention in the profession. However, working environment is inconsistently measured in the literature, hampering cumulation of knowledge. This article develops the first validated teacher-report measure of working environment. Theory and empirics were synthesised to define relevant constructs, then focus groups, expert consultation and cognitive interviews with teachers were used to generate and refine items. The resulting questionnaire displayed the hypothesised factor structure in two samples of teachers. The scale also showed strong predictive validity and the results help resolve a puzzle around the importance of workload in the existing empirical literature. Through improved measurement, the scale can help identify steps by which school leaders can improve retention.