Purpose In obstructive sleep apnea (OSA), hypoxia secondary to apnea and hypopnea and the resulting systemic inflammatory response are the main causes of comorbidities. The aim of this study was to investigate the relationship between OSA and vimentin, which plays an important role in the activation of cells that synthesize inflammatory cytokines. Materials and Methods The study included 150 OSA patients (50 mild, 50 moderate, and 50 severe OSA) and 50 patients without OSA as a control group. Plasma vimentin levels were measured from peripheral blood samples using a commercial enzyme-linked immunosorbent assay (ELISA) kit. Results The OSA patients in our study had significantly higher body mass index, apnea-hypopnea index (AHI), triglyceride level, mean oxygen desaturation, and plasma vimentin levels compared to the healthy control group (p = 0.007, 0.001, 0004, 0.001, and 0.001, respectively). Plasma vimentin level was significantly higher in the moderate and severe OSA groups compared to the control and mild OSA groups (p = 0.001 for all). There was no difference between severe and moderate OSA. There were significant correlations between plasma vimentin levels and OSA patients' AHI and mean oxygen desaturation (r = 0.46, p = 0.001; r = 0.214, p = 0.005). Conclusion In this study, we observed significant positive correlations between plasma vimentin level and OSA severity, weight, AHI, and mean oxygen desaturation. Vimentin may have utility as a biomarker in the follow-up and treatment of OSA.