Background: Primary brain malignancy is distinct from other oncologic diagnoses in its presentation and course. Recent treatment advances have modestly improved survival; yet, prognoses for afflicted patients remain grim, which often leads to non-oncology providers questioning the pertinence of aggressive critical care in this population. By relating patient and disease factors with mortality rates in malignant brain tumor (MBT) patients admitted for critical care, we seek to identify valuable prognostic factors and clarify the expected outcomes following intensive care unit (ICU) admission among these patients. Methods: A single-institution retrospective review was performed of 80 primary MBT patients admitted to neuro- or medical ICUs over a five-year period. The Electronic Health Record (EHR) was queried to identify MBT patients who had been admitted to the ICU. Patients undergoing planned surgical resection or with post-operative complications were excluded, as were patients with brain metastases. A matched control group of 80 solid tumor (ST) patients (excluding brain tumors) was included for comparison. Similar aged matched controls were randomly identified via EHR over the same time period to include non-brain, ST patients admitted to the ICU. Demographic, oncologic, and admission data were related to outcomes, which included complication rates (ICU mortality, six-month mortality) and change in Karnofsky Performance Status (KPS) score. Results: The average age was 55.9 (20-83) and 62.8 (27-89) years in the MBT and ST group, respectively (p = 0.10). ICU mortality was 15% and 21% (p = 0.411) and six-month mortality was 46% and 65% (p = 0.10) in the MBT and control groups, respectively. The most common reasons for ICU admission were seizures (36%) and septic shock (21%) among MBT patients, compared to hypoxic respiratory failure (43%) and septic shock (30%) among ST patients. The MBT group’s KPS score decreased by 23.6 ± 26.82 during their ICU admission, while the control group KPS decreased by 27.0 ± 28.3 (p = 0.87). Average length of ICU stay was 3.82 ± 4.4 days in the MBT group, compared to 2.95 ± 1.83 days in the control ST group (p = 0.29). Average length of hospital stay was 9.07 ± 9.0 days in the MBT group and 8.67 ± 7.76 days in the ST group (p = 0.92). Conclusions: No significant difference was observed in ICU or 6-month mortality when comparing primary MBT and ST patients. Change in KPS score across ICU admissions was similar among the two groups. Our data indicate that despite their guarded prognosis, MBT patients fare no worse than those with other solid tumor types at our institution in the critical care setting. These similarities in mortality and functional scores justify medical ICU admission in patients with primary brain malignancy, and should inform intensivist and oncologist admission patterns.