Leadership is an important part of any business. It's a very complex, and yet, insufficiently explored area. There is a great number of theories and approaches to leadership. Both in practice and in literature, great emphasis is placed on the importance of successful leadership, primarily concerning the role of the leader. To succeed as a leader, one must posess a specific set of virtues. Their traits, attitudes and beliefs, but also how they treat their followers in certain situations - are of key importance. In recent years, successful leadership has been the topic of many seminars and guidebooks aiming to educate and train leaders in various areas of business and everyday life. But, much like acquiring information without assessing it critically, attending seminars and reading books on leadership without applying that knowledge both in real life and business is a fruitless effort. A leader must be motivated to be able to motivate others, his followers. So where does the motivation come from? A successful leader's driving force comes from the spiritual harmony. In other words, the leader needs to have faith, love, hope and will, both for the work performed, and for those who follow. The premise is that the leader has to achieve a state of spiritual harmony to be successful in what he does. The emphasis is on personal growth, which is the main condition of achieving such spiritual state. In this thesis, spiritual harmony in leadership is explained through a case study of St. Vinko Paulski, the founder of a highly successful church movement called Sisters of Mercy.