The mortality and prognostic factors for patients admitted to the intensive care unit (ICU) with solid tumours are unclear The aim of this study was to describe demographic, clinical and survival data and to identify factors associated with mortality in critically ill patients with solid tumours. A prospective observational cohort study of 177 critically ill patients with solid tumours admitted to a medical-surgical oncological ICU was undertaken. There were no interventions. Among the admissions, 66% were surgical, 79.7% required mechanical ventilation during their stay in the ICU and 31.6% presented with severe sepsis or septic shock. In a multivariate analysis, independent prognostic factors for in-ICU death were the need for vasopressors (OR: 22.66, 95% confidence interval: 6.09 to 82.22, P < 0.001) and the acute physiology and chronic health evaluation (APACHE) II score (OR: 1.92, 95% confidence interval: 1.43 to 2.58, P < 0.001). Cox multivariate analysis identified the length of stay in the ICU, Charlson comorbidity index score greater than 2, and the need for vasopressors as independent predictors of death after ICU discharge. The mortality rate in the ICU was 21.4%. Improved outcomes in critically ill cancer patients extended to the subgroup of patients with solid tumours. Independent prognostic factors for in-ICU death were the need for vasopressors and the APACHE IL score, while the length of stay in the ICU, Charlson comorbidity index score >2, and the need for vasopressors were independent predictors of death after ICU discharge.