To examine the prevalence of cognitive frailty and identify its influencing factors among in older patients with lung cancer undergoing chemotherapy.A cross-sectional study was conducted between January and August 2024 among 304 older patients with lung cancer undergoing chemotherapy at a tertiary hospital in Chengdu, China. Data were collected using a general information questionnaire, the FRAIL Scale, the Mini-Mental State Examination (MMSE), the Hospital Anxiety and Depression Scale (HADS), and the Nutritional Risk Screening 2002 (NRS 2002). Binary logistic regression was performed to identify independent risk factors associated with cognitive frailty.A total of 304 older patients with lung cancer undergoing chemotherapy finished the investigation. The prevalence of cognitive frailty was 26.3% (80/304). In the initial phase of analysis, 13 independent variables were selected from 23 candidate variables through univariate analysis. Subsequent binary logistic regression analysis revealed that age, monthly household income per capita, employment status, health insurance type, cancer stage, anxiety, depression, nutritional risk, and daily exercise duration were independently associated with cognitive frailty.The prevalence of cognitive frailty is high among older patients with lung cancer undergoing chemotherapy and is influenced by multiple factors. Therefore, screening for cognitive frailty should be considered in clinical practice, with particular focus on elderly patients, those with low income, and those in advanced stages of the disease. It is crucial to take into account the patients' physiological, psychological, and behavioral factors when designing and implementing multimodal, individualized intervention strategies, aiming to effectively prevent and alleviate cognitive frailty.© 2025. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.