Despite successful discharge from the intensive care unit (ICU), a substantial number of patients remain at risk of ICU readmission or death. Identifying high-risk individuals at the time of ICU discharge is essential for planning post-ICU care. This study aimed to assess the Clinical Frailty Scale (CFS) at ICU discharge as a screening tool for predicting ICU readmission and post-ICU mortality, and to compare its predictive performance with other commonly used scoring systems. We conducted a retrospective single-center study including adult patients (≥20 years) discharged from all ICUs to general wards. Patients discharged for non-recovery purposes were excluded. Within 24 hours of ICU discharge, clinical scores: Acute Physiology and Chronic Health Evaluation II, Modified Early Warning Score, National Early Warning Score, Sequential Organ Failure Assessment (SOFA), and CFS, were assessed. The primary outcome was a composite of ICU readmission or all-cause mortality after ICU discharge. Univariate and multivariate logistic regression analyses were performed to identify independent predictors. A total of 648 patients were included. ICU readmission or post-ICU mortality occurred in 6.5% of patients. Compared to others, these patients had significantly higher Charlson Comorbidity Index scores (P = .002), more frequent delirium (P < .001), and received more intensive interventions such as mechanical ventilation or high-flow oxygen (P < .001), vasopressors (P < .001), and hemodialysis (P < .001). In multivariate analysis, both SOFA score (P < .001) and CFS score (P = .002) remained independent predictors of adverse outcomes. CFS demonstrated the highest discriminative ability (area under the curve, 0.788) compared to SOFA (0.722), Acute Physiology and Chronic Health Evaluation II (0.718), National Early Warning Score (0.725), and Modified Early Warning Score (0.695). The CFS assessed at ICU discharge is a simple, accessible, and effective tool for predicting ICU readmission and post-ICU mortality. Compared to other commonly used scores, CFS demonstrated favorable predictive performance and may serve as a practical option for routine discharge planning and risk stratification in post-ICU care.