Purpose: This study aimed to investigate the predictive value of circulating irisin levels in discriminating the presence and severity of obstructive sleep apnea (OSA) in obese individuals. Methods: This study was conducted on obese volunteers with and without OSA. All volunteers underwent polysomnography. Blood samples were taken on the day of the test. In addition to routine biochemistry studies, irisin levels were determined by enzyme-linked immunosorbent measurement. ROC analysis was performed to determine the predictive value of irisin. Results: Of 100 volunteers, 75 had OSA and 25 did not. Irisin levels were significantly lower in the group with OSA than in the non-OSA group. The lowest irisin levels were determined in the group with severe OSA. Irisin levels showed high sensitivity and specificity in distinguishing between OSA and non-OSA groups. It had high sensitivity and specificity in differentiating severe OSA from other groups in subgroups, while it had low sensitivity and specificity in differentiating patients with mild and moderate OSA. In logistic regression analysis, a low irisin level was determined to be a risk factor for OSA independent of BMI. Conclusion: This study indicated that irisin levels decrease in obese individuals with OSA, correlating with the severity of the condition. Additionally, irisin levels may act as an independent predictor for OSA. The predictive value of irisin in identifying severe OSA among obese patients suggests its potential as a promising biomarker.