<p>Frailty is common among patients undergoing maintenance hemodialysis (MHD) and is associated with adverse health outcomes. This study aimed to develop and validate a nomogram for estimating frailty probability in patients undergoing MHD. Data collected from January to June 2025 at four hemodialysis centers in Nanchong City were used to construct the training and internal validation cohorts. Data collected from July to December 2025 at two additional hemodialysis centers in Nanchong City were used for external validation. A total of 1034 patients undergoing MHD were included, comprising 566 patients in the training cohort, 242 in the internal validation cohort, and 226 in the external validation cohort. Frailty was defined according to the Fried frailty phenotype. Candidate variables were selected using least absolute shrinkage and selection operator regression, and variables with non-zero coefficients were included in multivariable logistic regression for coefficient estimation and nomogram construction. The nomogram was evaluated using discrimination, calibration, decision curve analysis, and internal and external validation. The final nomogram included five readily available variables: NRS 2002, CCI, living arrangement, physical activity, and depressive symptoms. The nomogram showed good discrimination in the training, internal validation, and external validation cohorts, with area under the curve values of 0.886, 0.821, and 0.837, respectively, and demonstrated satisfactory calibration and potential clinical utility. This nomogram may help estimate the probability of frailty among patients undergoing MHD and support healthcare providers in identifying individuals who may benefit from further comprehensive frailty assessment during routine care.</p>