A long-term sports training induces morphological and functional changes in the cardiovascular system, with the activation of angiogenesis being one of the most significant ones. Aim: The aim of the study was to assess the impact of an 8-month sports training on the serum levels of vascular endothelial growth factor and the physical performance in young athletes. Material and methods: A total of 28 sports middle school students (athletics faculty) aged 13 years, including 14 boys and 14 girls, were included in the study. All participants underwent clinical assessment at each stage of the study. Electrocardiographic and echocardiographic examinations were performed. Furthermore, the levels of vascular endothelial growth factor were measured and a cardiac stress test was performed, the outcome of which was used to calculate the physical working capacity (PWC₁₇₀). Results: There was a statistically significant decrease (274.3 ± 195.7 vs. 193.8 ± 153.8 ng/ml, p < 0.001) in the serum levels of vascular endothelial growth factor during the 8-month sports training. The levels were significantly lower in male athletes both at baseline (196.2 ± 157.3 vs. 352.4 ± 204.0 ng/ml, p = 0.02), and at the end of the observation period (139.6 ± 110.9 vs. 247.9 ± 174.6 ng/ml, p = 0.003). In the same period, the average PWC₁₇₀ value increased throughout the study group (108.6 ± 28.1 vs. 119.0 ± 34.1 W, p = 0.02), and sex-related statistically significant changes occurred only on the male group of athletes. No statistically significant correlations were found between the relative changes in the levels of vascular endothelial growth factor and the PWC₁₇₀ index (Spearman’s rank correlation coefficient – Rs 0.158, p > 0.05). Conclusions: Long-term sports training results in a decrease in the levels of vascular endothelial growth factor. At the same time, physical efficiency improvement is observed, which may suggest the involvement of adaptive, exerciseinduced angiogenesis in the skeletal muscles. However, the observed changes show distinct differences depending on the sex.