Abstract Background Between March 18^th and May 13^th 2020, the COVID-19 pandemic outbreak in Finland resulted in the closure of schools and the limitation of daycare (i.e. lockdown). Social distancing changed the daily routines of children with type 1 diabetes (T1D). Healthcare professionals were forced to adapt to the pandemic by replacing physical outpatient visits with virtual visits. However, the influence of the lockdown on glycemic control in these patients remained unknown. Methods In this retrospective register study from a pediatric diabetes outpatient clinic, we analyzed the glycemic data of T1D patients (n = 245; aged 4 to 16 years) before and under the lockdown. All the participants used continuous glucose monitoring (rtCGM or iCGM), two-thirds were on insulin pumps (CSII), and one-third on multiple daily insulin injections (MDI) therapy. Results In our patient cohort, time in range (TIR, n = 209) and mean glucose levels (n = 214) were similar prior to and under the lockdown (mean change 0.44% [95%CI: -1.1–2.0], p = 0.56 and -0.13 mmol/mol [95%CI: -0.3–0.1], p = 0.17, respectively). However, children treated with CSII improved their glycemic control significantly during the lockdown: TIR improved on average 2.4% [0.6–4.2] (p = 0.010) and mean blood glucose level decreased -0.3 mmol/mol [-0.6-(-0.1)] (p = 0.008). The difference was more pronounced in girls, adolescents and patients using conventional insulin pumps. Conclusions The glycemic control in T1D children did not deteriorate under the lockdown, and patients on CSII even improved their control, which suggests that social distancing might have allowed families to use the insulin pump more accurately as out-of-home activities were on hold.