Background: Abnormal sleep architecture with decreased rapid eye movement sleep and arousals during the periods of nocturnal oxygen desaturation (NOD) are seen in patients with chronic obstructive pulmonary disease (COPD) with significant consequences. This study was done to evaluate the prevalence of NOD and other sleep-related disorders in COPD patients. Patients and Methods: This prospective cross-sectional study was conducted in the sleep laboratory of our tertiary center over 1 year. Fifty COPD patients were enrolled in this study. They were classified into mild COPD and moderate COPD, according to the Global Initiative for Obstructive Lung Disease (GOLD) classification. Complete history, physical examination, and relevant laboratory investigations were taken. All patients were subjected to overnight polysomnography. Results: Eight patients had mild COPD, whereas 42 patients had moderate COPD. Mean sleep efficiency was decreased with an average of 71.08% with a significant difference between mild and moderate COPD cases. Minimal SpO2, average SpO2, SpO2 <90%, and duration of SpO2 <90% in the study group showed mean values of 80.77%, 94.33%, 3.93%, and 12.09 min, respectively, with a mean respiratory disturbance index (RDI) of 2.45. NOD was seen in 18% (9 patients) and overlap syndrome was seen in 12% (6 patients) in our study. Forced expiratory volume in 1 s and SpO2 were found to have statistically significant difference (P < 0.05) between patients with respect to NOD. It correlated well with body mass index (BMI) and neck circumference with RDI and also overlap syndrome. Conclusions: NOD is related to the degree of respiratory dysfunction and can coexist with overlap syndrome. Occurrence of overlap syndrome can be predicted with the help of BMI and RDI.