Some studies indicate the role of TNF-α, IL-6, and IL-8 in the development of endometriosis. However, a comprehensive assessment of plasma, peritoneal, and endometrioma fluids of proinflammatory cytokine concentrations in women with ovarian endometriosis has not yet been performed. Therefore, this study aimed to analyze plasma, peritoneal, and endometrioma fluids for selected proinflammatory cytokine concentrations in women operated on for ovarian endometriosis. A retrospective study was conducted with 56 women who underwent surgery for ovarian endometriosis. Body mass, height, and waist circumference were measured, as well as BMI being calculated. Plasma, peritoneal, and endometrioma fluids' interleukin-6 (IL-6), IL-8, and tumor necrosis factor-alpha (TNF-α) were determined by ELISA. Levels of IL-6 and TNF-α were significantly higher in endometrioma fluid compared to plasma and peritoneal fluid. In addition, levels of IL-6 and TNF-α were significantly higher in peritoneal fluid than found in plasma. Levels of IL-8 did not significantly differ between plasma and both peritoneal and endometrioma fluids, or between peritoneal and endometrioma fluids. There were also positive correlations among IL-6, IL-8, and TNF-α levels in endometrioma and peritoneal fluids (ρ = 0.29; < 0.05; ρ = 0.51; < 0.001; ρ = 0.52; < 0.001, respectively). There were no associations between cytokine levels in plasma, peritoneal, and endometrioma fluids and endometriosis stage. Plasma IL-8 levels can be considered an emerging biomarker of severity of local inflammation related to endometrioma. Further studies are needed for understanding the role of IL-6 and TNF-α as the markers of local inflammation in endometrioma.