This study worked to investigate the effect of household polluting fuel use (HPFU), as an indicator of household air pollution exposure, on frailty among older adults in rural China. Additionally, this study aimed to examine the moderating effect of healthy lifestyle behaviors on the aforementioned association. This study employed cross-sectional data from the 2018 Chinese Longitudinal Healthy Longevity Survey, which conducted nationally representative sampling of older adults from 23 provinces in mainland China. The frailty index was calculated using 38 baseline variables that assessed health deficits through questionnaire surveys and health examinations. A total of 4535 older adults aged 65 years and above were included in our study, among whom, 1780 reported using polluting fuels as their primary household cooking fuel. The results of regression analyses and multiple robustness checks indicated a significant increase in the frailty index due to HPFU. This environmental health threat was more profound among women, illiterate individuals, and low-economic-status groups. Moreover, healthy dietary and social activities had significant moderating effects on the association between HPFU and frailty. HPFU can be regarded as a risk factor for frailty among older adults in rural China, with its effects exhibiting socio-economic disparities. The adoption of healthy lifestyle behaviors can alleviate the frailty associated with HPFU. Our findings underscore the significance of using clean fuels and improving household air quality for healthy aging in rural China.