Objective To investigate the prevalence of cognitive impairment and identify its influencing factors among lung cancer patients undergoing chemotherapy, providing a scientific basis for targeted interventions. Methods A convenience sample of lung cancer patients receiving chemotherapy at West China Hospital, Sichuan University between April and October 2024 was enrolled. Data were collected using a general information questionnaire, the Mini-Mental State Examination, Nutritional Risk Screening 2002, Hospital Anxiety and Depression Scale, Barthel index, and FRAIL scale. Univariate analyses and multivariate logistic regression were performed to determine factors associated with cognitive impairment. Results A total of 380 patients undergoing chemotherapy for lung cancer were enrolled, and 205 (53.9%) of them had cognitive impairment. Univariate analyses revealed that there were statistically significant differences between the cognitively normal group and the cognitive impairment group in age, educational level, work status, nutritional status, Barthel index, and FRAIL scale score (P<0.05). Multivariate logistic regression showed that advanced age [odds ratio (OR)=1.045, 95% confidence interval (CI) (1.015, 1.075), P=0.002] and FRAIL scale score [OR=1.369, 95%CI (1.165, 1.609), P<0.001] were identified as independent risk factors for cognitive impairment, whereas higher educational attainment served as a protective factor, compared with patients with primary school education or below, patients with junior high school, high school/secondary vocational school, college, or undergraduate education and above had a lower risk of cognitive impairment [OR=0.437, 0.258, 0.243, 0.120, P<0.05]. Conclusions Cognitive impairment is highly prevalent among lung cancer patients undergoing chemotherapy and is significantly influenced by age, educational level, and frailty. Healthcare providers should develop targeted interventions based on these factors to reduce the prevalence of cognitive impairment.