Background As assessment tools of nutritional status, the controlling nutritional status (CONUT) and modified controlling nutritional status (mCONUT) score are associated with survival in various cancers. We aimed to investigate the association between the CONUT/mCONUT score's prognostic value and survival time in patients with FIGO stage IIB-IIIB cervical cancer treated with radiotherapy. Methods In this retrospective study, 165 patients between September 2013 and September 2015 were analyzed, and the optimal CONUT/mCONUT score cut-off values were determined using receiver operating characteristic curves. Propensity score matching (PSM) was used to minimize selection bias. The Kaplan-Meier method and a Cox proportional hazard model were used to assess the CONUT/mCONUT score's predictive value linked to survival time. Two nomograms were created to predict the overall survival (OS) and progression-free survival (PFS). Results The cut-off values for CONUT and mCONUT score were both 2. Five-year OS and PFS rates were higher in a low CONUT score group than in a high CONUT score group (OS: 81.1% vs. 53.8%, respectively, P < 0.001; PFS: 76.4% vs. 48.2%, respectively; P < 0.001). A high CONUT score was associated with decreased OS (hazard ratio (HR) 2.93, 95% CI 1.54-5.56; P = 0.001) and PFS (HR 2.77, 95% CI 1.52-5.04; P < 0.001). High CONUT scores influenced OS in the PSM cohort. A high mCONUT score was not associated with decreased OS and PFS in Cox regression analysis. Conclusion The CONUT score is a promising indicator for predicting survival in patients with cervical cancer receiving radiotherapy.