Cardiac rehabilitation (CR) improves clinical and functional recovery in older patients after acute cardiac syndromes, whose outcome is influenced by cardiac disease severity, but also by comorbidity and frailty. The aim of the study was to analyze the predictors of physical frailty improvement during the CR program. Data were collected in all patients aged > 75 years consecutively admitted from 1 January to December 2017 to our CR, consisting of 5-day-per-week of 30-min session of biking or calisthenics on alternate days for 4 weeks. Physical frailty was measured with short physical performance battery (SPPB) at the entry and the end of CR. Outcome was represented by an increase of at least 1 point in the SPPB score from baseline to the end of the CR program. In our study population of 100 patients, mean age 81 years, we demonstrated that a strong predictor of improvement in SPPB score was the poorer performance in the test at baseline; for Δ-1 point of score, we registered an OR 2.50 (95% CI = 1.64–3.85;p= 0.001) of probability to improve the physical performance at the end of CR. Interestingly those patients with worse performance at SPPB balance and chair standing task showed greater probability of ameliorating their physical frailty profile at the end of CR. Our data strongly suggest that CR program after acute cardiac syndrome produces a significant physical frailty improvement in those patients with worse frailty phenotype with an impairment in chair standing or balance at entry.