This study combined ambient air sampling and biomonitoring data to determine the PCDD/Fs exposure levels and health risk for residents near a Waelz plant. In total, 457 adults completed questionnaires and 48 subjects also gave blood samples. We used the USEPA multimedia model to estimate lifetime exposure and cancer risk. Analytical results show that average atmospheric PCDD/Fs concentrations were 149–285 fg I-TEQ/m3 and deposition flux was 0.57–116 pg I-TEQ/m2-d. The serum PCDD/Fs concentrations were from 5.30–50.91 WHO1998-TEQ with an average of 18.73 ± 10.05 pg/g lipid. The estimated lifetime average daily doses (LADDs) were 1.20 and 1.09 pg WHO1998-TEQ/kg/d, which are below the tolerable daily intake (TDI) range of 1–4 pg TEQ/kg bw (World Health Organization). However, the concentration was higher than concentrations for the general population in Taiwan. The USEPA multimedia model showed that the median of lifetime exposure to PCDD/Fs was 1.90 × 10–2 pg/kg bw/day and 3.19 × 10–2 pg/kg bw/day for Area U (upwind site) and Area D (downwind site), respectively. The carcinogenic risk was 2.96 × 10–6 (95th percentile = 1.61 × 10–5), and 4.97 × 10–6 (95th percentile = 2.59 × 10–5) for Area U and Area D, respectively. In summary, residents near the plant had a higher body burden of PCDD/Fs than the general population in Taiwan. The health risk from exposure, including cancer mortality caused by chronic exposure to PCDD/Fs, needs to be clarified further.