This study attempts to investigate the effectiveness of a strength-based coaching methodology in enhancing elements of the full range leadership model, especially transformational leadership. Transformational leadership is the process whereby leaders engage and influence their followers toward attaining a shared vision through their capacity to inspire, innovate and personalize their attention. A between-subjects nonequivalent control group design was used to explore the impact of strength-based coaching on transformational and transactional leadership behaviors measured in a 360-degree feedback process. Thirty-seven executives and senior managers from a large not-for-profit organization were nonrandomly assigned to either a coaching or waitlist cohort. The coaching cohort received six sessions of leadership coaching involving feedback on leadership and strengths, goal setting, and strengths development. The coaching protocol was manualized to ensure some methodological consistency between the 11 executive coaches providing the intervention. This involved providing a written manual to each coach and coachee that outlined the required coaching process for each session. After six sessions of coaching over 3 months, cohorts then switched roles. The results showed that participants experienced highly statistically significant increases in their transformational leadership behavior after coaching and this difference was perceived at all levels within the organization but not by the participants themselves. Adherence to the strength-based protocol was also a significant predictor of ultimate degree of change in transformational leadership behavior. The results suggest that strength-based coaching may be effective in the development of transformational leaders.