Background <p>The initiation of hemodialysis (HD) is a physiologically and functionally unstable period, often marked by abrupt fluid shifts, metabolic disturbances, and clinical decompensation. Frailty at HD initiation is associated with adverse outcomes. However, the link between unplanned dialysis initiation and frailty remains unclear. Because unplanned initiation often reflects insufficient predialysis care and acute systemic decline, it may be associated with frailty status at initiation.</p> Methods <p>This single-center cross-sectional study enrolled 93 patients with end-stage renal disease who initiated HD between September 2022 and September 2024. Frailty was assessed using the Japanese version of the Cardiovascular Health Study (J-CHS) criteria. The primary exposure was dialysis initiation type (planned versus unplanned). Prevalence ratios (PR) for frailty were estimated using modified Poisson regression. Sensitivity analyses included analyses excluding the weight-loss component, reanalysis using the Clinical Frailty Scale, and additional adjustment for delayed rehabilitation initiation.</p> Results <p>Frailty prevalence at dialysis initiation was 51.6%. It was significantly higher in the unplanned group than in the planned group (74.2% versus 40.3%, <i>p</i> = 0.002). Unplanned initiation was significantly associated with frailty (PR 1.65; 95% confidence interval [CI] 1.04–2.62).</p> Conclusions <p>Unplanned dialysis initiation was significantly associated with a higher prevalence of frailty at dialysis initiation. These findings suggest that patients undergoing unplanned initiation may represent a subgroup with a particularly high frailty burden at the time of dialysis transition, supporting the clinical importance of frailty assessment at dialysis initiation.</p>