Objectives were to describe the severity of illness in patients with leukemia or lymphoma urgently admitted to pediatric intensive care and explores the risk factors for mortality. A secondary analysis was performed of prospectively collected data from a cluster-randomized controlled trial in 21 children's hospitals from 2011 to 2015. Eligible patients were urgently admitted to intensive care and had a diagnosis of leukemia or lymphoma. Associations with intensive care mortality (primary outcome) were determined with multivariable generalized estimating equation with a logit link, accounting for clustering by site. Associations with time to intensive care mortality (secondary outcome) were determined with multivariable proportional hazards models. A total of 109 patients were included, age 115 (interquartile range [IQR] 42, 168) months and intensive care length of stay was 3 (IQR 2, 6) days. During the first hour in intensive care 36 (33%) were ventilated, and during intensive care 45 (41.3%) had at least 1 technology day. Day 1 Pediatric Logistic Organ Dysfunction (PELOD) score was ≥ 20 in 37 (33.9%), Pediatric Index of Mortality 2 mortality risk was > 10% in 35 (32.1%), and Children's Resuscitation Intensity Scale (RISC) was ≥ 3 (late admission to intensive care) in 32 (31.7%). Intensive care mortality was 20/109 (18.3%); with intensive care stay ≥ 20 days mortality was 51%. Previous urgent pediatric intensive care unit (PICU) admission, mechanical ventilation, and day 1 PELOD score were associated with higher PICU mortality. Mechanical ventilation, day 1 PELOD score, and late admission to the PICU (RISC ≥ 2) were associated with time to death. Patients with leukemia and lymphoma urgently admitted to intensive care had mortality of 18.3%, an improvement from historical cohorts. Risk factors were not accurate enough to make individual patient care decisions.