The main objective of this scientific study is the systematical arrangement of the average monthly streamflow in the Republic of North Macedonia by using adequate methodology. The river streamflow patterns in North Macedonia have yet to undergo comprehensive analysis, leaving a critical gap in our understanding of their dynamics and potential impact on water resource management. This study aims to address this knowledge deficit by conducting a thorough investigation of river streamflow patterns in the region, shedding light on their variability, trends, and implications for sustainable water resource planning. The prevailing pattern of the streamflow regime in North Macedonia was defined according to their monthly data, for the period 1961–2010, using Principal Component Analysis (PCA) and Agglomerative Hierarchical Clustering (AHC), using Ward’s agglomerative method and Euclidean distance. In this paper, the analysis involved processing data collected from 30 hydrological gauging stations situated along 22 perennial streams. After the PCA analysis, the factor loadings classification was carried via AHC. It results with three different patterns and five sub-patterns. The first pattern (R1) covers the northwestern part of the country, located in the high mountains Šar Mountain, Korab-Deshat, Jakupica Mountain and the Ohrid-Prespa Region. It features strong a magnitude in late spring with 25 percent of the total annual streamflow in May and a minimum in late September. The first half of the summer is still relatively rich in water. The second pattern (R2) covers the largest north, northeastern and southern part of the country (Kriva Reka catchment, Middle Povardarie and Pelagonia Basin) with a not so extreme maximum during April (16 % of the total streamflow) and drier summers with the minimum during August. The third pattern (R3) covers a smaller area and is located in the southeastern part of the country (Strumitsa-Radovish Basin). It contains gauging stations with an earlier maximum during March to April (each around 15 %) and the minimum during August to September, where the annual streamflow amplitude is much lower compared to other regions. From the two main streamflow drivers, snowmelt influence is less significant going eastward, while the rainfall influence is much stronger going eastward.