Persistent halogenated organic compounds, including polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), and dechlorane plus (DP), were determined in human serum collected in Weifang and Nanning, China, and the relationships between their concentrations and thyroid hormone concentrations were determined. The total PBDE (Σ10PBDEs), total PCB (Σ14PCBs), and total DP (ΣDP) concentrations were higher in Weifang (medians 220, 4.3, and 2.2 ng/g lipid, respectively) than in Nanning (medians 180, 1.9, and 1.5 ng/g lipid, respectively). The donors’ ages correlated with Σ14PCBs but not with Σ10PBDEs or ΣDP in Weifang. Age positively correlated with Σ10PBDEs but not Σ14PCBs and ΣDP in Nanning. The correlations between the individual PBDE, PCB, and DP congener and thyroid hormone concentrations were analyzed by stepwise multiple linear regression after log2-transforming the variables. Triiodothyronine (T3) concentrations were associated with BDE-99 concentrations and ΣDP in Weifang but with BDE-153 concentrations and Σ10PBDEs in Nanning. A positive correlation was found, for the first time, between anti-DP and free-T3 concentrations in Weifang, but free-T3 concentrations correlated with PCB-118 and PCB-170 concentrations in Nanning. Thyroxine (T4) concentrations correlated with total dioxin-like PCB concentrations in Weifang but with PCB-156 concentrations in Nanning. No significant correlations were found between the analyte and free-T4 concentrations in Weifang, but negative correlations were found between free-T4 and total dioxin-like PCB and BDE-190 concentrations in Nanning. No significant correlations were found between the analyte and thyroid-stimulating hormone (TSH) concentrations in Weifang but negative correlations were found between Σ10PBDEs and the TSH concentrations in Nanning. The correlations between the analyte and thyroid hormone concentrations followed different trends in Weifang and Nanning but were similar to those that have been found in animal and epidemiological studies.