Interest in studying the determinants that affect budget transparency is growing both in the world and in the Republic of Croatia. Budget transparency enables citizens to value the work of government at the local and state levels, to contribute to the budget process themselves and to gain a better insight into the financial situation. The aim of this paper was to determine and analyze the determinants of budget transparency of 128 Croatian cities. Observed budget transparency index OLBI is measured by the number of published key budget documents on the websites of local units and it takes values in the range from 0 to 5. Poisson's regression examines the impact of six selected variables: mayor's gender, income per capita, surplus / deficit per capita, income, estimated population and unemployment rates on the level of budget transparency of Croatian cities. The results indicate that only income per capita has statistically significant affect the level of budget transparency in Croatian cities, which confirms one of the set hypotheses. Budget transparency in the Republic of Croatia is increasing, but still there remains the challenge and incentive for better education and greater involvement of citizens in the entire budget process.