INTRODUCTION: Emergency department visits and hospitalizations for unsupervised medication exposures among young children increased in the early 2000s. Prevention efforts were initiated in response. METHODS: Nationally representative data from the National Electronic Injury Surveillance System-Cooperative Adverse Drug Event Surveillance project collected from 2009 to 2020 were analyzed in 2022 to assess overall and medication-specific trends in emergency department visits for unsupervised exposures among children aged ≤5 years. RESULTS: From 2009 to 2020, there were an estimated 677,968 (95% CI=550,089, 805,846) emergency department visits for unsupervised medication exposures among children aged ≤5 years in the U.S. Most visits involved children aged 1-2 years (2009-2012 [70.3%], 2017-2020 [67.4%]), and nearly one half involved prescription solid medications (2009-2012 [49.4%], 2017-2020 [48.1%]). The largest declines in estimated numbers of annual visits from 2009-2012 to 2017-2020 were for exposures involving prescription solid benzodiazepines (-2,636 visits, -72.0%) and opioids (-2,596 visits, -53.6%) and over-the-counter liquid cough and cold medications (-1,954 visits, -71.6%) and acetaminophen (-1,418 visits, -53.4%). The estimated number of annual visits increased for exposures involving over-the-counter solid herbal/alternative remedies (+1,028 visits, +65.6%), with the largest increase for melatonin exposures (+1,440 visits, +421.1%). Overall, the estimated number of visits for unsupervised medication exposures decreased from 66,416 in 2009 to 36,564 in 2020 (annual percentage change= -6.0%). Emergent hospitalizations for unsupervised exposures also declined (annual percentage change= -4.5%). CONCLUSIONS: Declines in estimated emergency department visits and hospitalizations for unsupervised medication exposures from 2009 to 2020 coincided with renewed prevention efforts. Targeted approaches may be needed to achieve continued declines in unsupervised medication exposures among young children.