In the North Sea and adjacent North Atlantic coastal areas fish experience relatively high levels of persistent organic pollutants. The aim of this study is to compare the mode of actions of environmentally relevant concentrations of halogenated compounds and their mixtures in Atlantic cod. Juvenile male cod were fed mixtures of chlorinated (PCBs, DDT analogs, chlordane, lindane and toxaphene), brominated (PBDEs) and fluorinated (Perfluorooctanesulfonate/PFOS) compounds for one month. One group received a mixture of all three compounds. Transcriptome analysis of liver samples was performed to identify the main affected pathways. Accumulated levels of chemicals in cod liver reflected concentrations found in wild fish. Pathway analysis revealed that the treatment effects by each of the three groups of chemicals (chlorinated, brominated and fluorinated) converged on activation of the unfolded protein response (UPR). The results of our transcriptomics analysis suggest that the UPR pathway is a sensitive common target of halogenated organic environmental pollutants