We present data to confirm that the island of La Palma harbours the first established feral population of ferrets Mustela furo on the Canary Islands in the Atlantic Ocean. It is not known when the species was introduced but individuals occasionally lost during hunting appear to have become established sometime in the previous 2 decades. Sightings of ferrets are mainly in the north of the island but they are likely to expand their range southwards, and a few have already been detected in the centre of the island. We report a total of 45 cases of wild ferrets in 28 different localities during 1998–2007. To minimize effects on native species, control measures or eradication are required. Public awareness of the problem and education campaigns, especially among hunters, are needed to reduce the threat of this alien species to the biota of the Canary Islands.