Objective: Frailty is a state of physiological vulnerability and associated with adverse outcomes. People experiencing homelessness and addiction have a higher burden of frailty than the general population. This study’s aim was to test the feasibility and impact of an exercise intervention with protein supplementation to target low physical functioning and frailty in this population, which was flexibly delivered over 12 weeks, with exercise options three days per week. Methods: The primary outcome of feasibility was measured by recruitment, retention, adherence, acceptability and adverse events. Secondary outcomes were physical function, pain, frailty and nutritional status, and self-reported health. Results: Forty-three participants enrolled. Overall retention was 69.8%, with higher retention observed in subgroups (women and older adults). Programme adherence and acceptability was reported in 93% and 100% of participants, respectively. No adverse events occurred. At baseline, sub-normative values were demonstrated for limb strength and balance; pain was prevalent in 34.8%; 23% had poor nutritional health between 32.5% and 72.1% lived with some degree of frailty. Significant improvements were demonstrated for lower limb strength, gait speed, pain, nutritional status and frailty, (p<0.05). Conclusions: This novel intervention delivered to this hard-to-reach population was shown to be feasible and impactful, indicating proof of concept.