Background: Malnutrition is common in patients undergoing hemodialysis and is a powerful predictor of morbidity and mortality. This study aimed to investigate the effect of nutritional status on permanent catheter patency in elderly patients aged >75 years of age undergoing dialysis using tunneled dialysis catheters; Methods: Records of 383 patients whose nutritional factors and body cell mass (BCM) were measured simultaneously at the start of dialysis between 14 January 2020 and 30 September 2023, at Chungnam National University Hospital, were retrospectively reviewed. The relationships between permanent catheter patency at 180 days and BCM parameters and clinical parameters were studied using Kaplan-Meier survival curves and multivariate Cox proportional hazards analysis. Results: Age and sexual differences were significant (p ≤ 0.05), and most of the BCM parameters and BCM were not significant (p ≤ 0.05), except for intracellular water. Permanent catheter patency was superior at low controlling nutritional status (CONUT) scores (p < 0.05). After adjustment for covariates, the CONUT score remained an independent factor associated with permanent catheter-patency survival; Conclusions: CONUT scores measured before the start of dialysis are expected to play an important role in predicting the prognosis of permanent catheter-patency survival in patients aged >75 years.