River discharge and its variations are often the subject of research from different aspects. This study aims to examine the discharge variability of selected rivers in central Serbia and the northern part of Montenegro, which belong to the Danube River basin (Black Sea Drainage basin). In general, all these rivers have uneven water regimes, a large share of evaporation in the water balance during the year, and very low values in discharges in the summer. In this regard, an analysis of mean annual and monthly discharge changes in ten hydrological stations from nine rivers in the 1961–2020 period was made. By using the t-test, a comparison of two 30-year periods (1961–1990 and 1991–2020) was made to examine if there were significant changes in the discharges. The obtained results indicate that in all rivers, annual discharge decreased in the second period compared to the earlier one, and a statistically significant decrease is recorded in 3 rivers, Lepenica, Lugomir and Lim. Changes in monthly discharges between the two 30-year periods are statistically very significant in the summer period in the selected rivers of Montenegro. In contrast they are not statistically significant in selected rivers of Serbia, with several exceptions in spring and autumn. The obtained results indicate mainly a statistically significant discharge decreasing in the second period, which is primarily correlated with a significant increase in air temperature. As discharge changes influence water resource management, the results obtained in this study are important for decision-makers.