The hazards posed to terrestrial wild mammals by plastics are poorly documented.  A questionnaire designed to gather evidence on entanglement was therefore sent to wildlife rehabilitation centres identified from an internet search. It was also publicised on social media. Responses were received from 44 organisations, and related to 156 individual admissions owing to plastic entanglement. Most of these cases were the European hedgehog (Erinaceus europaeus) 89% (n = 139 (95% CI, 83%, 93%), with a smaller proportion involving red foxes (Vulpes vulpes) 5% (n = 8 (95% CI, 2%,9%); badgers (Meles meles) 2% (n = 3 (95% CI, 0.3%, 4%); and deer (unknown species) 4% (n = 6 (95% CI 1.7%, 8%). Death, or euthanasia because of the severity of the injuries, was the outcome for 41% (n = 68 (95% CI 36%, 51%) of the reported cases. Although some reporting bias is possible, with centres with positive cases being more likely to respond, the results indicate that substantial numbers of wild terrestrial mammals in Britain are affected by plastic entanglement, with fatal outcomes for many.