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Background: The coexistence of obstructive sleep apnea (OSA) and chronic obstructive pulmonary disease (COPD) is termed “Overlap syndrome (OS).” Objectives: The present study aimed at estimating the prevalence of OS among patients diagnosed with OSA. Methods: It was a prospective observational study conducted on patients presenting to respiratory medicine outpatient department (sleep clinic) with symptoms of sleep-disordered breathing and was found to have OSA by overnight polysomnography. These patients were then subjected to spirometry to diagnose COPD. Results: The prevalence of OS in the study population was found to be 41.3%. Excessive daytime sleepiness was found to be higher in overlap group patients (P = 0.033), the difference was statistically significant. The mean age (59.9 ± 9.6 years) was found to be high in the OS group compared to those without the same. The mean forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and FEV1/FVC (pre- and postbronchodilator) spirometry parameters were found to be lower in patients with OS. Conclusion: The study showed that the prevalence of OS in the present study was 41.3%. Excessive daytime sleepiness and age >60 years were risk factors for OS in a patient with OSA. OS patients had lower pulmonary function values.