This study investigated the fate of polybrominated diphenyl ethers (PBDEs) in a thermal treatment system that was employed to recover the metals from the electric arc furnace (EAF) fly ash. After 1450°C thermal treatment, the content of PBDEs in the EAF fly ash (50128 ng/kg) was greatly reduced by 98.9%, based on the solid destruction efficiency (SDE). The sums of five PBDE contents in ingot and slag were 86.0 and 32.3 ng/kg, respectively, revealing that the residual PBDE content in slag was much lower than those in woodland (180 and 710 ng/kg) and grassland (440 ng/kg) soils (Harrad and Hunter, 2006). With this PBDE level, the slag can be either safely disposed of in landfills or utilized as construction material. After the 1450°C thermal treatment and 1200°C secondary combustion, 95.8% of the PBDEs were destroyed or removed without air pollution control devices (APCDs). The PBDE concentrations in cooling unit and filter (APCDs) were 8810 and 327 pg/Nm3, respectively, while that in the PUF cartridges (final emission) was 13009 pg/Nm3. However, the PBDE concentration of the untreated flue gas was 22.1 ng/Nm3, which is still higher than that measured in the exhausts from various stationary sources (15.7–46.7 ng/Nm3) (Wang et al., 2010a, c). Fortunately, the concentration of PBDEs can be effectively reduced to a much lower level (13.0 ng/Nm3) in the flue gas. In addition, after the Pearson correlation analyses, the logarithm contents of PBDEs and PCDD/Fs showed a statistically high correlation (r = 0.930–1.000). Consequently, thermal treatment with APCDs can effectively reduce the PBDEs in EAF fly ash, while the heavy metals can also be recovered.