Mental disorders among the pediatric population are a major area of public health concern. Little is known regarding changes in pediatric hospital resource use related to mental health (MH) long after the onset of the COVID-19 pandemic in March 2020. To assess rates and trends of hospitalizations and emergency department (ED) visits related to MH and self-harm (SH) among children before and during the 3 years following the pandemic onset. This cross-sectional study used national hospital data. The study sample included all MH- and SH-related hospitalizations and ED visits among children aged 6 to 17 years in France between January 1, 2016, to May 31, 2023. Interrupted time-series analysis of monthly rates of MH- and SH-related hospitalizations and ED visits per 100 000 children was conducted to assess changes before and every year after the pandemic onset. Rate ratios (RRs) between estimated and expected rates were calculated. Overall, 583 244 hospitalizations (81.4% for MH and 18.6% for SH) and 432 725 ED visits (79.9% for MH and 20.1% for SH) were analyzed. The mean (SD) age of the children was 13.7 (2.9) and 14.8 (1.7) years for MH-related and SH-related hospitalizations, respectively, and 14.2 (2.6) and 14.6 (2.1) years for MH-related and SH-related ED visits, respectively. For MH-related hospitalizations, 52.6% were female and 47.4% were male; for SH-related hospitalizations, 83.1% were female and 16.9% were male. For MH-related ED visits, 62.8% were female and 37.2% were male; for SH-related ED visits, 77.4% were female and 22.6% were male. Before the pandemic, an increasing trend in all monthly rates, except that of MH-related hospitalizations, was observed. After an immediate decrease in hospitalization and ED visit rates during the initial pandemic period (March 1 to May 31, 2020), trends increased in the first 2 years following the pandemic onset and decreased thereafter. Overall, rates of MH-related hospitalizations and ED visits exceeded expected rates in only the second year after the pandemic onset, with increases of 6.0% (RR, 1.06 [95% CI, 1.05-1.06]) and 5.0% (RR, 1.05 [95% CI, 1.04-1.05]), respectively. However, rates of hospitalizations and ED visits for behavioral syndromes (mainly eating and sleeping disorders) persistently exceeded expected rates, with increases of 29.0% (RR, 1.29 [95% CI, 1.25-1.34]) and 26.0% (RR, 1.26 [95% CI, 1.21-1.31]) in the third year, respectively. Likewise, rates of SH-related hospitalizations and ED visits persistently rose above expected rates, with increases of 29.0% (RR, 1.29 [95% CI, 1.26-1.32]) and 43.0% (RR, 1.43 [95% CI, 1.40-1.47]) in the third year, respectively. In this cross-sectional study, persistent increases in the use of hospital resources to treat eating and sleeping disorders and intentional SH among pediatric patients were observed long after the onset of the COVID-19 pandemic. These findings warrant future research to identify persistent stress factors in children.