Background: Stroke is a leading cause of disability worldwide, resulting in long-term impairments requiring rehabilitation. Frailty, characterized by reduced physiological reserve and vulnerability to stressors, is associated with poor health outcomes. When assessed using the Clinical Frailty Scale (CFS), frailty has been linked to adverse outcomes; however, its role in stroke rehabilitation remains underexplored. This study investigates the impact of pre-stroke frailty on functional recovery during inpatient stroke rehabilitation. Methods: A retrospective cohort study was conducted on 206 stroke patients admitted between 2020-2022. Pre-stroke frailty was assessed using the CFS, and rehabilitation outcomes were measured using Functional Independence Measure (FIM) gain and efficiency. Differences across CFS categories, stroke location, age, and sex were statistically analyzed. Results: Among these patients, 42.7% were female, and 75.7% were aged 60 or above. There were no significant differences in FIM gain or efficiency across CFS categories (p > 0.05). Frailty was associated with lower admission (p = 0.041) and discharge (p = 0.032) FIM scores. Conclusions: Pre-stroke frailty, assessed retrospectively using the CFS, does not predict functional improvement or efficiency during inpatient rehabilitation. However, frailty was associated with poorer functional status at admission and discharge. All patients meeting the admission criteria benefited from rehabilitation, regardless of frailty level.