The European Commission requested the EFSA Panel on Plant Health to perform a pest categorisation of Diaporthe vaccinii Shear, the fungal agent responsible for twig blight, canker, viscid rot, fruit rot and storage rot of several Vacciniumspecies. The pest is listed in Annex IIAI of Directive 2000/29EC. D. vaccinii is a single taxonomic entity and methods exist for its discriminative detection. The host is restricted to Vaccinium species, the main cultivated hosts being blueberries and cranberries. Hosts are cultivated throughout Europe, and wild Vaccinium species are common components of forests. Conditions are conducive to disease development in most areas of Europe, but not in all Member States (MSs). The disease is currently present in Latvia with restricted distribution and the pest is under surveillance in The Netherlands. In the one Latvian report, storage losses were observed on cranberry, but these losses were caused by a complex of pathogens, including D. vaccinii, which was isolated with a low incidence. Detection methods are available but cultural and morphological identifications should be confirmed with molecular tools owing to the presence of other Phomopsis species on Vaccinium in Europe. The pathogen can spread via the movement of (asymptomatic) infected or contaminated host plants for planting. No information exists on any methods applied for the control of D. vaccinii in the EU. D. vaccinii does not have the potential to be a quarantine pest as it does not fulfil one of the pest categorisation criteria defined in International Standard for Phytosanitary Measures No 11, that of having a severe impact. Data are not sufficient to conclude on pest categorisation of D. vaccinii based on the criteria of the International Standard for Phytosanitary Measures No 21 because there is no information about the level of potential consequences as a result of the use of infected host plants for planting.