The prognosis for patients with hematological malignancies (HMs) admitted to the intensive care unit (ICU) is poor. The objective of this study was to evaluate the clinical characteristics and hospital outcomes of critically ill patients with HMs admitted to an oncological ICU. This is a prospective, observational cohort study. A total of 102 patients with HMs admitted to ICU from January 2008 to April 2011 were included. Univariate and multivariate logistic regressions were used to identify factors associated with hospital mortality. During the study period, 3,776 patients with HM were admitted to the Department of Hematology of the Instituto Nacional de Cancerología located in Mexico City, Mexico. After being evaluated by the intensivist, 102 (2.68 %) patients were admitted to the ICU. The ICU mortality rates for patients who had two or less organ system failures and for those with three or more organ system dysfunctions were 20 % (5/25) and 70.1 % (54/77), respectively (P < 0.0001). A multivariate analysis identified independent prognostic factors of in-hospital death as neutropenia at the time of ICU admission (odds ratio (OR), 4.24; 95 % confidence interval (CI), 1.36-13.19, P = 0.012), the need for vasopressors (OR, 4.49; 95 % CI, 1.07-18.79, P = 0.040), need for invasive mechanical ventilation (OR, 4.49; 95 % CI, 1.07-18.79, P = 0.040), and serum creatinine >106 μmol/L (OR, 3.21; 95 % CI, 1.05-9.85, P = 0.041). The ICU and hospital mortality rates were 46.1 and 57.8 %, respectively. The independent prognostic factors of in-hospital death were the need for invasive mechanical ventilation, the need for vasopressors, serum creatinine >106 μmol/L, and neutropenia at the time of ICU admission.