Type 1 diabetes mellitus (T1D) incidence in children varies across regions and countries, showing a continuous rise globally. Chile has mandatory T1D notification and guaranteed access to diagnosis and treatment since 2005, providing a strong model to evaluate T1D epidemiology. To determine T1D incidence in Chilean population under 20 years between 2006 and 2014. We reviewed mandatory notifications of T1D in Chile's public health system. A total of 4153 T1D cases in population under 20 years were notified from 2006 to 2014. Median age was 14 years and 51% were male. The average annual T1D incidence was 12 per 100 000 population, with an increase from 10.2 in 2006 to 13.8 in 2014 (β 0.5 95% confidence interval [CI] 0.4-0.7, P < .001). A significantly increasing linear trend of T1D incidence was observed in groups of 0 to 4 years (β 0.33, 95% CI 0.06-0.59, P = .02), 5 to 9 years (β 0.68 95% CI 0.27-1.10, P = .006), and 10 to 14 (β 0.94, 95% CI 0.67-1.20, P < .001), but increase was less pronounced in the oldest children aged between 15 and 19 years (β 0.22, 95% CI -0.03 to 0.44, P = .052). The lowest regional T1D incidence was observed in the Araucanía region, which has the highest rate of indigenous population. Incidence rates of T1D in Chile, evaluated through a mandatory notification program, are rapidly increasing in children and adolescents. If increasing trends persist, Chile will reach T1D incidence rates of Western developed countries in the next decade. © 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.