COVID-19 associated public health measures and school closures exacerbated symptoms in some children and youth with attention-deficit hyperactivity disorder (ADHD). Less well understood is how the pandemic influenced patterns of prescription stimulant use. We conducted a population-based study of stimulant dispensing to children and youth ≤ 24 years old between January 1, 2013, and June 30, 2022. We used structural break analyses to identify the pandemic month(s) when changes in the dispensing of stimulants occurred. We used interrupted time series models to quantify changes in dispensing following the structural break and compare observed and expected stimulant use. Our main outcome was the change in the monthly rate of stimulant use per 100,000 children and youth. Following an initial immediate decline of 60.1 individuals per 100,000 (95% confidence interval [CI] - 99.0 to - 21.2), the monthly rate of stimulant dispensing increased by 11.8 individuals per 100,000 (95% CI 10.0-13.6), with the greatest increases in trend observed among females, individuals in the highest income neighbourhoods, and those aged 20 to 24. Observed rates were between 3.9% (95% CI 1.7-6.2%) and 36.9% (95% CI 34.3-39.5%) higher than predicted among females from June 2020 onward and between 7.1% (95% CI 4.2-10.0%) and 50.7% (95% CI 47.0-54.4%) higher than expected among individuals aged 20-24 from May 2020 onward. Additional research is needed to ascertain the appropriateness of stimulant use and to develop strategies supporting children and youth with ADHD during future periods of long-term stressors.