The objective of this nationwide population-based cohort study was to evaluate the correlation between continuous glucose monitoring (CGM) use and glucose variability in pre-schoolers with type 1 diabetes. Methods: We analysed data from the Slovenian National Registry. The primary endpoint was the difference in glucose variability between periods, during which participants were using CGM and periods, during which CGM was not used, over 5 years. Results: A total of 40 children <8 years old were followed for an estimated observational period of 116 patient/years. Mean age at CGM initiation was 3.5 (±1.7) years. Both standard deviation of mean glucose [3.6 mmol/L (3.2-3.9) with CGM and 4.3 mmol/L (3.8-4.7) without CGM, p < 0.001] and coefficient of variation [44.0% (40.4-47.0) with CGM and 46.1% (42.3-49.4) without CGM, p = 0.021] were lower during the periods, when CGM was used. Frequent CGM use (>5 days/week) was associated with a 0.4% [4.4 mmol/mol] reduction in glycated haemoglobin level (7.6% compared to 7.2%, p = 0.047). Conclusions: Our results indicate that the use of CGM was associated with reduced glucose variability during a 5 year follow-up period among pre-schoolers with type 1 diabetes.