Background <p>This study examines the longitudinal effects of COVID-19 pandemic regulations on health-related quality of life (HrQoL), glycaemic control and lifestyle characteristics and describes the epidemiology of COVID-19 in children with type 1 diabetes (T1D).</p> Methods <p>This monocentric, prospective study included, from May to November 2020, pediatric outpatients up to 18 years with T1D. During the first 16 weeks, COVID-19–associated symptoms were assessed weekly, while HrQoL, COVID-19 affectedness and appraisal, screen time, and physical activity were assessed monthly. Body-mass-index standard deviation scores (BMI-SDS), HbA1c, and glycaemic monitoring data were collected at clinical visits three monthly. All parameters were reassessed at final visit after 10 months and assigned to the pandemic restriction phases. Estimates of correlation (est) were tested by a linear mixed-effects model.</p> Results <p>55 children with T1D were included, with a median age of 11 years and 56.4% male. HrQoL remained normal and stable throughout the pandemic, but showed significant associations with physical activity (est 3.63, <i>p</i> &lt; 0.01), screen time (est − 1.66, <i>p</i> &lt; 0.01) and financial situation (est − 9.15, <i>p</i> &lt; 0.05). During the pandemic, BMI-SDS increased (<i>p</i> &lt; 0.01), but mean HbA1c remained at about 7.5% and glucose time in range improved (<i>p</i> &lt; 0.01). During the lockdown phases, screen time tended to be highest (<i>p</i> &lt; 0.1), while physical activity was lowest (<i>p</i> &lt; 0.01). At baseline, one of 55 patients (1.8%) was COVID-19 seropositive from infection. At the study’s end 20.5% were positive from infection, and 4.9% from vaccination.</p> Conclusions <p>In children with T1D, HrQoL and metabolic control remained stable under pandemic regulations, but BMI-SDS and physical activity worsened. Continuation of outpatient care and opening of schools may have contributed to a healthy lifestyle and resilience.</p> Trial registration <p>Not applicable.</p>