In the present study, a single Arcanobacterium (A.) pinnipediorum strain isolated from discharge of a jaw swelling of a grey seal pup (Halichoerus grypus) in England, UK, was identified. This strain was further characterized by phenotypical investigations, by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), by Fourier transform infrared spectroscopy (FT-IR), and genotypically by sequencing the 16S rRNA gene and the genes gap encoding glyceraldehyde 3-phosphate dehydrogenase, tuf encoding elongation factor tu, and rpoB encoding the β subunit of bacterial RNA polymerase. The present study gives a first detailed characterization of the species A. pinnipediorum from a grey seal in the UK. However, the route of infection of the grey seal with the bacterial pathogen remains unclear.