Adults who are homeless experience poor health and frequently require hospital in-patient care but the physical functioning ability of this group is rarely considered. The objective of this study was to evaluate a broad range of physical functioning variables to enable better future planning of targeted health and accommodation services for this group. This cross-sectional, observational study was conducted in a large acute hospital in Dublin, Ireland. A comprehensive ward-based test battery evaluated physical functioning in 65 in-patients registered as homeless with an age range of 23–80 years. Less than 10% (n = 5) were > 70 years. 58/65 (83%) of participants had mobility limitations and 35/65 (54%) reported at least one fall in the previous six months. Only 25/66 (35%) were able to walk for 6 min and 20/65 (31%) were able to climb one flight of stairs. 45/63 (70%) of participants were pre-frail or frail. Muscular mass was normal in the majority of participants but grip strength was low. This study revealed hospital in-patients registered as homeless displayed particularly poor physical functioning levels and mobility regardless of age. Health and housing services should address the unmet physical functioning needs of this vulnerable group.