A growing body of research supports the importance of supervisors’ safety leadership in promoting employees’ engagement in safety. However, the factors that give rise to these safety leadership behaviors are under-explored. The current study addressed this void by adopting a Job Demands-Resources framework to identify contextual influences on supervisors’ safety leadership behaviors. Focus group data from sixty-nine supervisors recruited from the UK construction industry showed that role overload, production demands, formal procedures, and workforce characteristics hindered supervisors’ engagement in safety leadership. In contrast, social support (especially from the organization and co-workers) and perceived autonomy promoted supervisors’ engagement in safety leadership. Exploration around these issues highlighted a need for more training for supervisors in this role and the development of a supportive environment between supervisors affiliated with different parent companies.