OBJECTIVES: To examine the effects of societal and public health changes during the COVID-19 pandemic in Sweden on children's body mass index (BMI) and to determine whether the effect persisted and differed between the sexes. STUDY DESIGN: We used growth curve models applied to retrospective cohorts of children in preschool, grade 4, grade 7, and the first year of high school between the years 2014 and 2023. The data include information on the BMI of individuals in these grades. RESULTS: The results indicate that the pandemic in Sweden was associated with a very small weight gaining effect among children, with no substantial differences between the sexes. The effect peaked approximately 2 years after the beginning of the pandemic, following which the BMI began trending back toward levels that would be expected had the pandemic not affected children's body weight. CONCLUSIONS: These study findings from Sweden partially align with those of international studies, although the effect is smaller in magnitude compared with international estimates. The results of this study suggest that more liberal restrictions, compared with stricter ones, are associated with a smaller excess increase in body weight among children.