Organizational citizenship behavior (OCB) is defined as performance that supports the social and psychological environment in which a task is conducted. Teachers' OCB can be directed toward particular individuals (OCBI) and/or toward the organization (OCBO). Despite their beneficial impact on school, these could entail personal costs for the teacher. The present study argues that OCB contributes to teachers' strain through the mediating impact of role overload, role ambiguity, and role conflict, while job autonomy buffers it. The structural equation modeling results from a sample of 483 Israeli teachers and their principals confirmed the main hypotheses for OCBO. Role overload and role ambiguity fully mediated the relation of OCBO to teachers' strain; the relation of OCBO to role stressors was significant for teachers with low job autonomy, but was non-significant for teachers with high job autonomy. This study opens an exploration of the positive and the negative consequences of OCB for teacher and school.