The present article reports on the results of a quantitative empirical survey of leadership styles of Slovenian entrepreneurs, owners and/or founders of SMEs. The study aimed to answer the following research question: Which leadership style enhances the success of a leader’s organisation? On the basis of the existing literature, we hypothesised that the transformational leadership style is likely to increase the effectiveness and success of a business. We also hypothesised that Slovenian entrepreneurial leaders used the transformational leadership style to a greater extent than the transactional leadership style. The survey was conducted using the self-reported Multifactor Leadership Questionnaire on a sample of 100 entrepreneurial leaders from the entire territory of Slovenia. The results suggest that Slovenian leaders use transformational leadership more than transactional. The use of transformational leadership was correlated with increased self-reported effectiveness of their organisation. The article concludes with a discussion on the impact of transformational leadership on enhancing the effectiveness of Slovenian business. Implications for future research are discussed.