The aim of this study was to analyze how line and middle managers experience and describe barriers and enablers in the implementation of a health-promoting leadership program in municipal organizations. A qualitative case study design was applied to examine the leadership program in a case involving implementation of an organizational health intervention. Data were mainly collected using semi-structured interviews with line and middle managers participating in the leadership program. Interviews with senior managers, notes from meetings/workshops, and written action plans were used as complementary data. The interview data were analyzed using a thematic analysis, and the complementary data using a summative content analysis. The findings show that the interviewed line and middle managers experienced this leadership program as a new approach in leadership training because it is based primarily on employee participation. Involvement and commitment of the employees was considered a crucial enabler in the implementation of the leadership program. Other enablers identified include action plans with specific goals, earlier experiences of organizational change, and integration of the program content into regular routines and structures. The line and middle managers described several barriers in the implementation process, and they described various organizational conditions, such as high workload, lack of senior management support, politically initiated projects, and organizational change, as challenges that limited the opportunities to be drivers of change. Taken together, these barriers interfered with the leadership program and its implementation. The study contributes to the understanding of how organizational-level health interventions are implemented in public sector workplaces.