Background The usual calculation of body mass index (BMI) can be misleading in patients with advanced chronic kidney disease (CKD) because their altered fluid balances may not be reflected. We obtained corrected BMI (cBMI) and corrected Geriatric Nutritional Risk Index (cGNRI) values and investigated whether the impedance ratio (IR) of 200/5 kHz, measured using bioimpedance spectroscopy, was associated with cGNRI in older patients with nondialysis CKD stage 5 (CKD5‐ND). Methods Patients over 65 years old (n = 118) were divided into groups by cGNRI tertiles. The differences between the correlations were tested using Steiger's z‐test. The IR and cBMI were used as both continuous and categorical variables in the regression analyses to determine the factors that were independently associated with the cGNRI. Results Patients in the third cGNRI tertile had a significantly lower mean IR than those in the other 2 tertiles (P < .001). Across the 3 cGNRI tertile groups, the IR was incrementally lower in the higher cGNRI tertiles (P for trend < .001). The Steiger's z‐test showed that the IR had a significantly stronger correlation with cGNRI than cBMI had with cGNRI. In the multivariable linear regression analyses, the IR was independently associated with the cGNRI, after adjusting for various confounders. Conclusion The current results revealed that the IR was a more sensitive indicator of nutrition risk than BMI and was independently associated with cGNRI in older patients with CKD5‐ND. Our study suggests that the IR is an appropriate tool for nutrition risk screening.