Aims/introduction COVID-19 pandemic and its associated circumstances had adversely afected patients with chronic diseases. This study aimed to assess the health-related quality of life (QoL), and identify its psychological and clinical correlates in patients with diabetes mellitus (DM) during pandemic in Egypt. Materials and methods A cross-sectional study, using a convenience sampling technique, was conducted among patients with DM who were recruited from Zagazig University endocrinology outpatient clinics, Sharkia Province, Egypt from June 30 to September 29, 2020. A total of 200 consecutive patients were interviewed using a semistructured demographic and clinical checklist, the fear of COVID-19 scale (FCV-19S), the Hospital Anxiety and Depression Scale (HADS), and the short form 36 (SF-36) health survey. Results Poor physical and mental QoL was reported in 64% and 62% of patients with DM, respectively. Female gender, increased mean arterial pressure (MAP), associated physical comorbidities, and depressive symptoms were associated with lesser odds of physical QoL (OR 0.46, 0.96, 0.29, and 0.88, respectively). Besides, female gender, associated physical comorbidities, fear of COVID-19 virus infection (FCV), and depressive symptoms were associated with lesser odds of mental QoL (OR 0.41, 0.36, 0.91, and 0.84, respectively). The FCV was inversely correlated with all items of SF-36 among patients. Conclusion QoL, either physical or mental, was adversely afected among patients with DM during pandemic. FCV was negatively correlated with all QOL domains. Longitudinal studies are warranted to explore the long-term efect of pandemic on the physical and mental well-being of patients with DM.