Background: The limited range of patients clinically responding to checkpoint inhibitor therapy (CIT) is of interest and requires studying the immunological mechanisms underlying this phenomenon. It also remains to be decided or better clarified which biomarkers should be considered when selecting patients for immunotherapy. The purpose of this study was to evaluate some parameters of the cytokine profiles of peripheral blood in melanoma patients receiving CIT with the disease progression. Methods: The study included 11 patients aged 47-82 years with advanced melanoma. CIT (nivolumab 3 mg/kg once every 14 days or 240 mg once every 14 days) continued until the appearance of reliable signs of the disease progression (in combination with symptomatic deterioration of the patient's condition). The levels of cytokines (TNF-α, IL-1ß, IL-2, IL-4, IL-6, IL-8, IL-10, IFN-γ) in the blood serum of patients were determined by ELISA before treatment, after 4 and after 8 injections. The results were expressed as specific content (units/mg). Results: All patients developed disease progression after immunotherapy. CIT was accompanied by different changes most pronounce after the 8^th CIT cycle. Levels of IL-1β, IFN-γ, IL-10 and α-TNF exceeded the values before CIT by 118%, 131%, 84% and 20%, respectively (5.2 [4.37; 6.1] versus 2.0 [0.44;4], p≤0.041, 3.9 [3.7;4.5] vs. 1.7 [0.5;3.5], p≤0.021, 6.5 [5.8 ;8.2] vs. 3.5 [3.2;5.4], p≤0.04; 4.1 [3.9;4.9] vs. 3.4 [3.2;3.9] pg/ml, p≤0.047). Levels of IL-6, on the contrary, decreased by the 8th CIT cycle by 32%: 5.1 [3.5; 6.1] versus 7.5 [6.2; 22.3] pg/ml, p≤ 0.045. Levels of IL-2 and IL-8 did not change. Conclusions: The revealed significant increase in levels of IL-1β, IFN-γ, IL-10 and α-TNF, as well as the IL-6 decrease, may indicate certain features of the cytokine profile of melanoma patients during the treatment, which may affect the imbalance of regulatory molecules and contribute to the disease progression.