Patients undergoing hemodialysis (HD) have significantly higher mean blood lead levels (BLLs) than those in healthy individuals. Because elementary lead can be found in particulate matter with a diameter of <2.5 μm (PM 2.5), this cross-sectional study was conducted to assess the effect of environmental PM 2.5 exposure and other clinical variables on BLLs in patients receiving HD. We recruited 921 patients on maintenance HD (MHD) who had undergone HD for at least 6 months and who had previously participated in a BLL study. Mean PM 2.5 concentrations in living environments in the previous 12 and 24 months were analyzed using a blood lead test. From a multivariate analysis, after adjustment for related factors, the mean PM 2.5 concentrations in the previous 12 and 24 months were positively associated with log BLLs. In addition, days with PM 2.5 levels exceeding the standard level during the previous 12 and 24 months were positively associated with log BLLs. Patients exposed to higher PM 2.5 concentrations and more days with PM 2.5 levels exceeding the standard level exhibited a higher prevalence of high and high-normal BLLs and a lower prevalence of low-normal BLLs. After adjustment for related variables, the BLLs exhibited a significantly positive association with environmental PM 2.5 in patients undergoing MHD.