This study evaluated the degree in which leadership training in the marketplace was effective at developing authentic leadership and at changing individual behaviour. Theories of change were integrated in the current study. A conceptual model combining Authentic Leadership Development (ALD) theory and the Theory of Planned Behaviour (TPB) was proposed. Furthermore, this study explored the relationship between a positive contemplation of change and the actual change observed in individuals after the leadership intervention. This longitudinal quasi-experimental study surveyed managers in one of four leadership development programmes (2 corporate & 2 business-school programmes). Analyses showed that leaders who attended a leadership intervention (vs. control group) developed higher levels of authentic leadership. The results also indicated that intentions were developed through the interventions and that the development of such intentions translated into changes in authentic behaviour. Intentions mediated the relationship between attitude and authentic leadership.