Abstract: BACKGROUND: The coronavirus disease 2019 (COVID-19) lockdown had a significant effect on people’s lifestyles and dietary habits resulting in a possible negative health impact, particularly for patients with type-2 diabetes mellitus (T2DM). The objective of the study was to assess the changes in dietary habits and lifestyle and how these relate to glycemic control in patients with type 2 diabetes (T2D), who attended Zagazig Diabetes Clinic, Sharkia Governorate, Egypt, during the COVID‑19 pandemic. MATERIALS AND METHODS: A total of 402 patients with T2D were included in this cross‑sectional study. A semistructured questionnaire was used to collect information on socioeconomic status, dietary habits, lifestyle changes, and previous medical history. Weight and height were also measured, and hemoglobin A1C levels before and after lockdown were compared. Data analysis was performed using the SPSS. To determine statistical significance, Chi‑square test was used for categorical variables whereas, paired t‑test or McN-Nemar test, as appropriate, was used to compare change in HbA1c before and after lockdown. Ordinal logistic regression was used to determine factors associated with weight change, whereas binary logistic regression was used to determine factors related with glycemic control. RESULTS: During the COVID‑19 pandemic, 43.8% of the studied groups consumed more than their usual diet with an increase in fruits, vegetables, and immunity‑boosting food; 57% depended on home‑cooked food, 48.3% did not practice exercise. About 57% reported to have gained weight, 70.9% suffered from mental stress, and 66.7% reported inadequate sleep. Collectively, there was a statistically significant decrease in the percentage of good glycemic control in the studied groups (28.1% vs. 15.9%) before and after the COVID‑19 lockdown, respectively (P < 0.001). Weight gain, physical inactivity, mental stress, and inadequate sleep were significantly associated with poor glycemic control. CONCLUSION: COVID‑19 pandemic has had a negative impact on the lifestyle and dietary habits of the studied groups. Therefore, it is very important to ensure better diabetes management in this critical period. Keywords: COVID‑19, dietary habits, lifestyle, type 2 diabetes mellitus