OBJECTIVE: Our study aimed to investigate the relationship between the number of teeth remaining and cognitive impairment among Chinese older adults, and to explore the role of low body weight in this association. METHODS: Data were drawn from 2011 to 2014 surveys of the Chinese Longitudinal Healthy Longevity Survey (CLHLS), involving 4056 respondents who had no cognitive decline and aged ≥ 65 years at baseline. Cognitive function was measured by the Mini-Mental Status Examination (MMSE), and the cognitive impairment was classified according to the length of education. Number of natural teeth was self-reported (classified as ≥ 20, 10-19, 1-9, and 0). Low body weight was defined as having a body mass index (BMI) of less than 18.5 kg/m RESULTS: Comparing with participants with ≥ 20 teeth, 10-19 teeth and 1-9 teeth, those with 0 teeth (HR:2.14, 95% CI: 1.51, 3.03) were significantly associated with higher cognitive impairment risk in the fully adjusted model. Compared with denture users, the fully adjusted HR (95% CI) for non-denture users was 1.33 (1.04, 1.70). no teeth with non-denture users had the highest cognitive impairment risk (HR:1.63, 95% CI: 1.10, 2.41). Low body weight mediated 6.74% (ranging from 3.49 to 11%) of the association between the number of teeth remaining and cognitive impairment. CONCLUSION: Tooth loss increases the risk of cognitive decline, and low body weight partially mediates this association. CLINICAL TRIAL NUMBER: This is a retrospective cohort study targeting a population survey, which does not involve clinical trials and does not have clinical trial numbers.