Objective: The aim of this study was to explore the school principal's role in promoting physical activity for inactive children in school settings. Design: Exploratory qualitative interview study. Setting: The study was conducted in seven elementary schools in central Sweden. Method: Data were collected by means of semi-structured interviews with eight school principals. Theories of bioecology and teacher agency informed the study and shed light on the environmental factors and resources affecting school principals' efforts to promote physical activity for inactive children. Result: The most common strategy school principals described was to delegate responsibility for planning organised activities to dedicated school personnel working with the children. In their leadership role, principals described having the power and opportunity to recruit school personnel with positive attitudes towards promoting physical activity, which likely increases inactive children's opportunities to engage in PA. Conclusion: When provided the adequate resources, and by virtue of their management position within the school, principals have the opportunity to make a difference to promote PA for inactive children. Delegating responsibility to school personnel may however create unequal PA opportunities, and if there are no initiators dedicated to this work, inactive children may be left out of PA opportunities in school.