Frailty is common among older people and results in adverse health outcomes. We investigated whether exposure to PM2.5 is associated with frailty. This cross-sectional study involved 20,606 community-dwelling participants aged ≥ 65 years, residing in New Taipei City, Taiwan. Analytic data included phenotypic frailty, disease burden by Charlson Comorbidity Index (CCI), urban or rural residence, and household income. PM2.5 exposure was calculated from air quality monitoring records, with low exposure defined as the lowest quartile of the study population. 1,080 frail participants (5.2%) were older, predominantly female, had more comorbidities, lived rurally, and had low PM2.5 exposure (all p < 0.001). In multinomial logistic regression analyses, the likelihood of high PM2.5 exposure was higher in prefrail (OR 1.4, 95% CI 1.3-1.5) and frail adults (OR 1.5, 95% CI 1.2-1.9) than in robust individuals, with stronger associations in those who were male (frail: OR 2.1, 95% CI 1.5-3.1; prefrail: OR 2.2, 95% CI 1.9-2.6), ≥ 75 years old (frail: OR 1.8, 95% CI 1.3-2.4; prefrail: OR 1.5, 95% CI 1.3-1.8), non-smokers (frail: OR 1.6, 95% CI 1.3-2.0; prefrail: OR 1.4, 95% CI 1.2-1.5), had CCI ≥ 2 (frail: OR 5.1, 95% CI 2.1-12.6; prefrail: OR 2.1, 95% CI 1.2-3.8), and with low household income (frail: OR 4.0, 95% CI 2.8-5.8; prefrail: OR 2.7, 95% CI 2.2-3.3). This study revealed a significant association between PM2.5 exposure and frailty, with a stronger effect in vulnerable groups.