Team-based work structures have become prevalent in science. Scientific teams, however, are characterized by competing individual-level and team-level needs (i.e., by mixed-motive situations). This makes leading scientific teams particularly challenging: Balancing competing individual-level goals and common team-level goals requires a specific type of leadership that simultaneously considers both satisfying individual-level needs as well as team-level needs. The current study addresses this issue by combining the dual-focused model of transformational leadership with person-environment fit theory. Specifically, we investigated needs-supplies fit, person-supervisor fit, and team fit as mediators of the relationship between transformational leadership and scientific team members’ job satisfaction and work-related strain. In doing so, we provide a new perspective on leadership in scientific teams by explicitly differentiating individual-level and team-level effects of transformational leadership. We tested our hypotheses using a three-wave design with a sample of 134 members of 42 scientific teams. The relationships between individual-focused transformational leadership, job satisfaction, and work-related strain were mediated by needs-supplies fit and person-supervisor fit. Team-focused transformational leadership was positively related to job satisfaction and negatively related to work-related strain. Our findings contribute to further clarifying the mechanisms underlying the relationship between transformational leadership and members’ well-being in scientific teams.