OBJECTIVES: To describe the proportion of pediatric mental health emergency department (MH-ED) visits across 5 COVID-19 waves in New York City (NYC) and to examine the relationship between MH-ED visits, COVID-19 prevalence, and societal restrictions. METHODS: We conducted a time-series analysis of MH-ED visits among patients ages 5 to 17 years using the INSIGHT Clinical Research Network, a database from 5 medical centers in NYC from January 1, 2016, to June 12, 2022. We estimated seasonally adjusted changes in MH-ED visit rates during the COVID-19 pandemic, compared with predicted prepandemic levels, specific to each COVID-19 wave and stratified by mental health diagnoses and sociodemographic characteristics. We estimated associations between MH-ED visit rates, COVID-19 prevalence, and societal restrictions measured by the Stringency Index. RESULTS: Of 686 500 ED visits in the cohort, 27 168 (4.0%) were MH-ED visits. The proportion of MH-ED visits was higher during each COVID-19 wave compared with predicted prepandemic trends. Increased MH-ED visits were seen for eating disorders across all waves; anxiety disorders in all except wave 3; depressive disorders and suicidality/self-harm in wave 2; and substance use disorders in waves 2, 4, and 5. MH-ED visits were increased from expected among female, adolescent, Asian race, high Child Opportunity Index patients. There was no association between MH-ED visits and NYC COVID-19 prevalence or NY State Stringency Index. CONCLUSIONS: The proportion of pediatric MH-ED visits during the COVID-19 pandemic was higher during each wave compared with the predicted prepandemic period, with varied increases among diagnostic and sociodemographic subgroups. Enhanced pediatric mental health resources are essential to address these findings.