Background: The relationship between sleep disorders and diabetes is bidirectional; sleep disorders can raise the risk of developing insulin resistance, while diabetes would worsen sleep quality. Objectives: Assessment of the prevalence and severity of sleep apnea among patients with type II diabetes mellitus. Patients and Methods: a prospective cross-sectional study was carried out on 45 cases with type II diabetes mellitus that were either admitted in Aswan University hospital or sought medical advice in the out-patient clinics during the period from 2017 to 2019. For every patient, the demographic and clinical data were collected, blood glucose levels and HBA1c were measured and full night attended polysomnography was done. Results: 77.78% of the diabetic cases had sleep apnea syndrome. The most common pattern was obstructive sleep apnea (82.86%). Apnea hypopnea index, obstructive sleep apnea and mixed sleep apnea were considerably higher among cases who had clinical picture of neuropathy compared to those without clinical picture of neuropathy. There was a moderate positive correlation between HbA1c with both AHI (P =0.005, r= 0.464) and obstructive sleep apnea (P value 0.016, r= 0.405). Furthermore, there was a mild positive correlation between HbA1c and percentage of time spent with oxygen saturation <90% (TST< 90%) (P =0.022, r =0.385). Conclusion: The prevalence of sleep apnea and its severity is high among patients with type II diabetes mellitus.