This study examines the relationship between supervisors’ transformational leadership behaviors and their work groups’ subsequent affective well-being and job satisfaction under specific moderating conditions (collective efficacy and perceptions of meaningful work). Longitudinal data from 42 work groups in a Canadian government organization was used to test the proposed relationships. Work groups’ collective efficacy has a significant moderating effect on the relationship between transformational leadership and positive group affective well-being. Specifically, groups with lower levels of collective efficacy exhibit a stronger relationship between transformational leadership behaviours and both affective well-being and job satisfaction.