One of the main goals of public sector reform in the Republic of Serbia is to develop professional capacity and create effective leadership. In general, effective leadership has a very significant role in public sector functioning. In addition, it is also important for the quality of public services that are delivered to citizens and other stakeholders. The aim of this research was to investigate the association between characteristics and behaviours of managers, which are internal factors influencing the process of effective leadership in the public sector. The research was conducted in the organizational units of the Sector for Human Resources of the Ministry of Interior of the Republic of Serbia on a sample of 50 respondents. The Spearman's rank correlation coefficient was used to determine the associations. The results of the research indicated that the authoritarian characteristics of managers are mostly related to directive behaviour of managers, i.e., a high positive correlation was calculated between authoritarian characteristics and directive behaviour of managers (r = 0.784, p < 0.001). Furthermore, the findings demonstrated that the charismatic characteristics of managers are mostly related to the transformational behaviour of managers, i.e., a very high positive correlation was calculated between charismatic characteristics and transformational behaviour of managers (r = 0.913, p < 0.001). The research results can provide guidelines for the development of professional capacity of the public sector and the creation of effective leadership at all levels in order to properly implement reforms.