The present study integrates role theory, social exchange, organizational citizenship, and climate research to suggest that employees will reciprocate implied obligations of leadership-based social exchange (e.g., leader-member exchange [LMX]) by expanding their role and behaving in ways consistent with contextual behavioral expectations (e.g., work group climate). Using safety climate as an exemplar, the authors found that the relationship between LMX and subordinate safety citizenship role definitions was moderated by safety climate. In summary, high-quality LMX relationships resulted in expanded safety citizenship role definitions when there was a positive safety climate and there was no such expansion under less positive safety climates. The authors also found that safety citizenship role definitions were significantly related to safety citizenship behavior. Implications for both social exchange theory and safety research are discussed.