Context and Objective: Hypovitaminosis D and frailty are common in the older population. We aimed to determine whether 25-hydroxyvitamin D [25(OH)D] concentrations are associated with frailty and mortality. Design: We conducted a prospective cohort study. Setting and Participants: Participants included 4203 older men aged 70–88 years in Perth, Western Australia. Main Outcome Measures: 25(OH)D was measured by immunoassay. Frailty was assessed with the 5-point FRAIL (fatigue, resistance, ambulation, illness, and loss of weight) scale. Mortality was determined from the death registry via the Western Australian Data Linkage System. Results: At baseline, 676 (16.1%) men were frail, as defined by having ≥3 deficits (FRAIL scale ≥ 3). In multivariate cross-sectional analysis, low vitamin D status, defined by the lowest quartile of 25(OH)D values (<52.9 nmol/L), was associated with increased prevalent frailty (odds ratio, 1.96; 95% confidence interval [CI], 1.52 to 2.52) in comparison to the highest quartile of 25(OH)D values (>81.6 nmol/L). After a mean period of 5.3 years, the adjusted odds ratio of being frail at follow-up for men with low vitamin D and having zero deficit at baseline (FRAIL scale = 0) was 1.56 (95% CI, 1.07 to 2.27). Low vitamin D also predicted all-cause mortality over a period of up to 9.2 years (hazard ratio, 1.20; 95% CI, 1.02 to 1.42), independent of baseline frailty and other covariates. Conclusion: Hypovitaminosis D is associated with prevalent and incident frailty in older men. Hypovitaminosis D also predicts all-cause mortality, independent of frailty. The association between vitamin D and mortality is not solely dependent on the occurrence of frailty.