PURPOSE: Geriatric Assessments (GAs) in older adults with cancer have informed treatment decision-making and refined survival prediction. However, little is known about the needs of older inpatients with cancer. Our objectives were to test the feasibility of a bedside GA, assess the prevalence of impairments in geriatric domains, determine how many were unknown to the medical team, and assess the impact of GA on patient care. METHODS: We conducted a cross-sectional observational single-centre pilot study. Structured GAs were performed on patients age 65+ admitted to the medical or radiation oncology inpatient wards at a tertiary care cancer centre. GA findings were shared with the patient's most responsible physician (MRP). RESULTS: 356 patients were screened, 39 were eligible and approached, and 37 were enrolled (recruitment rate 95%). Completion of the GA was possible in 92% of patients (34/37) and required a mean of 35 min. The mean number of geriatric domains impaired per patient was five (of seven assessed domains). The most common abnormal domains not known to the medical team were medication optimization (91%), cognition (90%), mood (69%), and social vulnerability (69%). MRPs responded to our survey for fifteen of thirty-three participants (45% response rate), and indicated that the GA results provided helpful information for patient management in 10 of 15 cases. CONCLUSION: Abnormal geriatric domains are common in older inpatients with cancer. Domains such as medication optimization, cognition, mood, and social vulnerability often go undetected and unaddressed. Identifying abnormal domains may improve the care of older inpatients with cancer.