OBJECTIVES: To evaluate the impact of ICU surge on mortality and to explore clinical and sociodemographic predictors of mortality. DESIGN: Retrospective cohort analysis. SETTING: NYC Health + Hospitals ICUs. PATIENTS: Adult ICU patients with coronavirus disease 2019 admitted between March 24, and May 12, 2020. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Hospitals reported surge levels daily. Uni- and multivariable analyses were conducted to assess factors impacting in-hospital mortality. Mortality in Hispanic patients was higher for high/very high surge compared with low/medium surge (69.6% vs 56.4%; p = 0.0011). Patients 65 years old and older had similar mortality across surge levels. Mortality decreased from high/very high surge to low/medium surge in, patients 18–44 years old and 45–64 (18–44 yr: 46.4% vs 27.3%; p = 0.0017 and 45–64 yr: 64.9% vs 53.2%; p = 0.002), and for medium, high, and very high poverty neighborhoods (medium: 69.5% vs 60.7%; p = 0.019 and high: 71.2% vs 59.7%; p = 0.0078 and very high: 66.6% vs 50.7%; p = 0.0003). In the multivariable model high surge (high/very high vs low/medium odds ratio, 1.4; 95% CI, 1.2–1.8), race/ethnicity (Black vs White odds ratio, 1.5; 95% CI, 1.1–2.0 and Asian vs White odds ratio 1.5; 95% CI, 1.0–2.3; other vs White odds ratio 1.5, 95% CI, 1.0–2.3), age (45–64 vs 18–44 odds ratio, 2.0; 95% CI, 1.6–2.5 and 65–74 vs 18–44 odds ratio, 5.1; 95% CI, 3.3–8.0 and 75+ vs 18–44 odds ratio, 6.8; 95% CI, 4.7–10.1), payer type (uninsured vs commercial/other odds ratio, 1.7; 95% CI, 1.2–2.3; medicaid vs commercial/other odds ratio, 1.3; 95% CI, 1.1–1.5), neighborhood poverty (medium vs low odds ratio 1.6, 95% CI, 1.0–2.4 and high vs low odds ratio, 1.8; 95% CI, 1.3–2.5), comorbidities (diabetes odds ratio, 1.6; 95% CI, 1.2–2.0 and asthma odds ratio, 1.4; 95% CI, 1.1–1.8 and heart disease odds ratio, 2.5; 95% CI, 2.0–3.3), and interventions (mechanical ventilation odds ratio, 8.8; 95% CI, 6.1–12.9 and dialysis odds ratio, 3.0; 95% CI, 1.9–4.7) were significant predictors for mortality. CONCLUSIONS: Patients admitted to ICUs with higher surge scores were at greater risk of death. Impact of surge levels on mortality varied across sociodemographic groups.