We aimed to assess the association between red blood cell distribution width (RDW) and mortality in patients enrolled by a Geriatric Department. One hundred twenty-two patients were followed up during 5 years. The primary end point was all-cause mortality, and hazard ratios were estimated using a Cox proportional hazard model. Higher RDW values were strongly associated with an increased risk of death. Survival curves across RDW quartiles were statistically different according to the log-rank test (p = 0.017). The first quartile presented higher probability of survival compared to the last one. The gradient from lower to higher risk across quartiles was clear both in the 5-year mortality risk and in the mortality rate per 100 person-years, which ranged from 18.9 to 42.6. However, in the Cox regression model after adjusting for age, severity, and other factors, excess risk was only observed in the highest RDW quartile, with a hazard ratio of 2.24 (CI(95%) 1.13-4.42) vs the first quartile. RDW is a good predictor of mortality in hospitalized older adults beyond those with cardiovascular risk factors, and it could serve as an integrative measure of multiple clinical and subclinical processes simultaneously occurring in complex patients.