To understand trends in U.S. cannabis-involved emergency department (ED) visits (i.e., those for which cannabis use was documented in the chief complaint or a discharge diagnosis) among young persons aged <25 years during the COVID-19 pandemic, CDC used National Syndromic Surveillance Program data to examine changes in ED visits during 2019-2022. Mean weekly cannabis-involved ED visits among all young persons were higher during the COVID-19 pandemic in 2020, 2021, and 2022, compared with corresponding periods in 2019. Large increases in cannabis-involved ED visits throughout the COVID-19 pandemic compared with prepandemic surveillance periods in 2019 were identified among persons aged ≤10 years. ED visit rates among children and adolescents aged 11-14 years did not differ by sex until the first half of the 2020-21 school year (2020, weeks 37-53), when ED visit rates among females surpassed those among males. Improving clinicians' awareness of rising cannabis-involved ED visits might aid in early diagnosis of cannabis intoxication among young persons. Further, increasing adults' knowledge regarding safe cannabis storage practices, strengthening youths' coping and problem-solving skills through evidence-based prevention programs, and modifying cannabis packaging to decrease appeal to youths might help prevent intentional and unintentional cannabis use.