A new method for the simultaneous detection of 20 polybrominated diphenyl ethers (PBDEs), 16 polycyclic aromatic hydrocarbons (PAHs), 4 hydroxyl PBDEs (OH-PBDEs) and 10 hydroxyl PAHs (OH-PAHs) in human hair has been developed for the first time. External target analytes from hair (hair-Ex) were ultrasonically extracted with acetone, while the internal target analytes (hair-In) were obtained with further digestion and liquid-liquid extraction of washed hair. Alkaline digestion with liquid-liquid extraction under alkaline and re-acidification combination conditions was the key procedure to successfully extract both parent and metabolic compounds from hair. Both external and internal extracts were purified with gel permeation chromatography, and the parent compounds were subsequently separated from their hydroxylated metabolites with a silica solid phase extraction column prior to instrumental analysis. GC-MS-MS, GC-MS and HPLC-MS-MS were used to analyze PAHs, PBDEs and their hydroxylated metabolites, respectively. The method showed satisfactory accuracy as well as precision, and the recoveries of PBDEs, PAHs, OH-PBDEs and OH-PAHs ranged from 62%-145%, 48%-135%, 60%-146% and 60%-88%, respectively. The developed method was validated in a pilot biomonitoring campaign. All parent analytes were approximately 100% detected in both hair-In and hair-Ex, while no OH-PBDEs were detected in hair-In and hair-Ex. All OH-PAHs were approximately 100% detected in hair-In with a mean Σ10OH-PAHs concentration of 174.7 ng per g dry weight (dw), and the concentration in hair-Ex was 18 times lower than that in hair-In with a relatively lower detection frequency. Both partial least squares discriminant analysis (PLS-DA) and Spearman correlation analysis with the concentration of analytes confirmed that the developed method performed well to distinguish the internal from external exposure to target analytes in hair.