Background: One third of bariatric surgery patients have an apnea–hypopnea index (AHI)>15/hr, representing moderate and severe forms of obstructive sleep apnea (OSA). Treating these forms of OSA is recommended to reduce the risk of perioperative complications. The AHI derived from poly(somno)graphy [P(S)G] is the gold standard for OSA diagnosis. However, performing P(S)G in all patients scheduled for bariatric surgery is time consuming and expensive. An accurate and simple screening tool able to rule out moderate to severe OSA would reduce the number of patients needing mandatory P(S)Gs. Objectives: To assess the validity of a simple sleep monitor (Checkme Health Monitor) as a screening tool for OSA in bariatric surgery patients. Setting: Obesity Center Amsterdam, OLVG-West, Amsterdam, the Netherlands Methods: Patients scheduled for bariatric surgery were prospectively enrolled in this study. All patients underwent preoperative P(S)G and simultaneously used the Checkme to assess the oxygen desaturation index. The diagnostic performance of the Checkme for AHI ≥15/hr was assessed using receiver operating characteristic curve analysis. Results: A total of 50 patients were analyzed. Sensitivity and negative predictive value were 100% and 100%, respectively, specificity and positive predictive value were 69% and 64%, respectively, for the optimal cutoff value of Checkme-3% oxygen desaturation index ≥9/hr for P(S)G-AHI ≥15. The area under the curve value expressed by the receiver operating characteristic curve was.95. Conclusion: The Checkme is valid for exclusion of moderate and severe OSA in bariatric surgery patients. The Checkme enables bariatric clinics not to perform P(S)G in all patients scheduled for bariatric surgery.