This master's thesis analyzes the macroeconomic effects of the Republic of Croatia's accession to the European Union during the first decade of membership. Using the synthetic control method, synthetic values for key macroeconomic indicators, including gross domestic product, components of aggregate demand, gross value added, labor productivity, and gross national income, were estimated for the period from 1997 to 2023.. The impact of EU membership on each of the macroeconomic indicators was assessed by comparing the deviations between actual and synthetic values. The research findings indicate significant positive effects of Croatia's EU membership, which intensify over time, with the most pronounced effects observed in the indicators for exports and imports of goods and services, household consumption, and NPISH, as well as gross national income. Despite certain limitations arising from the presence of idiosyncratic components, in the form of pronounced macroeconomic imbalances immediately prior to accession, the cumulative effects of membership are strong. Furthermore, the results of this analysis were confirmed through two placebo tests in time and a placebo test in space. Particular attention is given to the recent deepening of integration with the European Union, especially Croatia's entry into the Eurozone, whose anticipation effects may have significantly contributed to the marked intensification of positive outcomes recorded after 2020. These effects, along with the impact of Croatia's entry into the Schengen Area and the increased inflow of EU funds, represent one of the directions for future research.