Here, we report the results of petroleum component contamination assessment of the Temernik river and the Don river. Our aim was to study the hydrocarbon group content of petroleum components in the river water. Thus, we determined the mass concentrations of chemical oxygen demand, petroleum components, and aliphatic and polycyclic aromatic hydrocarbons. In the Temernik river, the concentrations of chemical oxygen demand, petroleum components, sum of aliphatic and polycyclic aromatic hydrocarbons were 21.4–34.4 mg/L, 0.14–6.0 mg/L, 10–18 μg/L, and 0.17–2.9 μg/L, respectively. The concentrations of chemical oxygen demand, petroleum components, and benzo[a]pyrene exceeded the maximum permissible concentration by 1.4–2.3, 2.8-120, and 1.3–5.8 times, respectively. In the Don river, the concentrations of chemical oxygen demand, petroleum components, sum of aliphatic and polycyclic aromatic hydrocarbons were 18.7-29.5 mg/L, 0.08- 0.16 mg/L, 8.2-12 μg/L, and 0.03-0.13 μg/L, respectively. The Severnoe reservoir was the less contaminated part of the river. The Temernik river estuary was the most contaminated part of the river. The pollutant concentrations increased in the Don River downstream of the Temernik river estuary. Therefore, the Temernik river influences on the Don river contamination. The chemical oxygen demand, petroleum components, and polycyclic aromatic hydrocarbons had the close distribution of concentrations in the rivers. However, the aliphatic hydrocarbon concentration changed in another way. The results of the study showed that the hydrocarbon groups of petroleum components can have different sources.