This master's thesis explores the accounting of nonprofit organizations, with a particular focus on its application in the context of county port authorities. The research aims to gain a deeper understanding of accounting in the nonprofit sector, emphasizing its key characteristics and role. In the theoretical part of the thesis, the nonprofit sector is analyzed, including the diversity of types and the specificities of their activities. Special emphasis is placed on the role of accounting within these organizations. A segment related to nonprofit organizations' accounting practices is also considered, investigating the methods of applying business records, accounting plans, and accounting documents. The importance of precise monitoring of financial activities in the nonprofit sector is highlighted. The structure of financial reporting in nonprofit organizations is also examined, encompassing the balance sheet, income statement, and accompanying notes to the financial statements. Through a practical example of the Port Authority of Rovinj, the specifics of accounting and financial reporting of county port authorities are explored. This example provides a better understanding of how theoretical concepts are applied in the real environment of nonprofit organizations. The conclusion of the thesis summarizes the key findings of the research and underscores the importance of accurate accounting for transparency, responsible management, and the financial sustainability of nonprofit organizations, including county port authorities.