Thirty alternative flame retardant compounds and a suite of 17 brominated diphenyl ether (BDE) congeners were determined in the blubber of 21 harbour porpoises stranded or bycaught around UK coasts during 2008 using GC-MS/MS. Of the 30 compounds, 19 were not detected. Of the remaining 11 compounds, some fell below the lowest calibration level and so were recorded as less than values, but were certainly present in the blubber samples (examples include tetrabromo-p-xylene (TBX), tetrabromo-o-chlorotoluene (TBCT) and 2,3-dibromopropyl-2,4,6-tribromophenyl ether (TBP-DBPE). Concentrations were low, the highest concentration being only 35μgkg−1 wet weight. This contrasted with those of the BDEs, summed concentrations which ranged from 54.6 to 913μgkg−1 wet weight, although levels in porpoise blubber have been declining since 1998. Both Dechlorane Plus (DDC-CO) isomers were detected in some samples, suggesting either that this product has been used in the UK or that its presence may result from atmospheric transport from source regions. BDE183, a marker for the octa-mix PBDE product, was found at low concentrations (0.63 to 1.7μgkg−1 wet weight) and the four nona- and deca-BDE congeners were not detected in any sample. •We have determined concentrations of 30 alternative flame retardants in porpoises•Of these, nineteen compounds were not detected•Concentrations were low, the highest being 35μgkg−1 wet weight (pentabromoethylbenzene)•Summed BDE concentrations were up to 1.0mgkg−1 lipid weight•Nona- and deca-BDE congeners were not detected