Population-level reports of suicide-related emergency department (ED) encounters among youth during the COVID-19 pandemic are lacking, along with youth characteristics and preexisting psychiatric service use. To characterize population-level and relative change in suicide-related ED encounters among youth during the COVID-19 pandemic compared with 2019. This cross-sectional study evaluated ED encounters in 2019 and 2020 at Kaiser Permanente Northern California-a large, integrated, community-based health system. Youth aged 5 to 17 years who presented to the ED with suicidal thoughts or behaviors were included. The COVID-19 pandemic. Population-level incidence rate ratios (IRRs) and percent relative effects for suicide-related ED encounters as defined by the US Centers for Disease Control and Prevention-recommended International Statistical Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) codes in 4 periods in 2020 compared with the same periods in 2019. There were 2123 youth with suicide-related ED encounters in 2020 compared with 2339 in 2019. In the 2020 group, 1483 individuals (69.9%) were female and 1798 (84.7%) were aged 13 to 17 years. In the 2019 group, 1542 (65.9%) were female, and 1998 (85.4%) were aged 13 to 17 years. Suicide-related ED encounter incidence rates were significantly lower in March through May 2020 compared with this period in 2019 (IRR, 0.57; 95% CI, 0.51-0.63; P < .001), then returned to prepandemic levels. However, suicide-related ED visits among female youth from June 1 to August 31, 2020, and September 1 through December 15, 2020, were significantly higher than in the corresponding months in 2019 (IRR, 1.19; 95% CI, 1.04-1.35; P = .04 and IRR, 1.22; 95% CI, 1.11-1.35; P < .001, respectively), while suicide-related ED visits for male youth decreased from September 1 through December 15, 2020 (IRR, 0.81; 95% CI, 0.69 to 0.94). Youth with no history of outpatient mental health or suicide encounters (129.4%; 95% CI, 41.0-217.8) and those with comorbid psychiatric conditions documented at the ED encounter (6.7%; 95% CI, 1.0-12.3) had a higher risk of presenting with suicide-related problems from September to December 2020 vs the same period in 2019. In this cross-sectional study of youth experiencing suicidal thoughts and behaviors, suicide-related presentations to the ED initially decreased during the COVID-19 pandemic, likely owing to shelter-in-place orders, then were similar to 2019 levels. However, a greater number of female youth, youth with no psychiatric history, and youth with psychiatric diagnoses at the time of the ED encounter presented for suicide-related concerns during the pandemic, suggesting these may be vulnerable groups in need of further interventions. Adjustments in care may be warranted to accommodate these groups during periods of crisis.