Transformational leaders employ a visionary and creative style of leadership that inspires employees to broaden their interest in their work and to be innovative and creative. There is some evidence that transformational leadership style is linked to employee psychological well-being. However, it is not clear whether this is due to (1) a direct relationship between leadership behaviour and affective well-being outcomes, or (2) a relationship between leadership behaviour and well-being that is mediated by followers’ perceived work characteristics. (Such characteristics include role clarity, meaningfulness, and opportunities for development.) This study aims to extend previous work by examining the validity of these two mechanisms in a longitudinal questionnaire study. The study was carried out within the elderly care sector in a Danish local governmental department. A theory-driven model of the relationships between leadership, work characteristics, and psychological well-being was tested using Structural Equation Modelling. The results indicated that followers’ perceptions of their work characteristics did mediate the relationship between transformational leadership style and psychological well-being. However, there was only limited evidence of the existence of a direct path between leadership behaviour and employee well-being. These findings have implications for design, implementation, and management of efforts to improve employee well-being.