The aim of this study was to determine whether early mobilization was associated with rehospitalization among elderly heart failure patients. We measured the time from admission to mobilization and other clinical characteristics for 190 heart failure patients (mean age, 80.7 years). The primary outcome was heart failure rehospitalization. Kaplan-Meier survival curves were plotted and the hazard ratios for rehospitalization were determined using Cox proportional hazards regression models. During a median follow-up period of 750 days, 58 patients underwent rehospitalization. The time from admission to mobilization was significantly longer for these patients than for those who were not rehospitalized. Univariate and multivariate Cox proportional hazards analyses showed that the time from admission to mobilization was an independent predictor of rehospitalization, and receiver-operating characteristic analysis determined an optimal cutoff value of 3 days for differentiating the patients more likely to experience a subsequent cardiac event (sensitivity, 76%; specificity, 69%; area under the curve, 0.667). Kaplan-Meier survival curve analysis showed a significantly lower event rate in the ≤ 3-day group (p = 0.001, log-rank test). In conclusion, the time from admission to mobilization may be one of the strongest predictors of rehospitalization in elderly heart failure patients. Early mobilization within 3 days may be an initial target for the acute phase treatment of heart failure.