Opisthobranch molluscs collected during the Sir Peter Scott Commemorative Expedition to the Pitcairn Islands (1991–2) are described. Twenty taxa were discovered from the four islands that form the group, and a further two species had been found during earlier work. The records of Phyllobranchillus orientalis and Peltodoris fellowsi represent considerable extensions to their known ranges. A large dendrodorid, provisionally referred to Dendrodoris tuberculosa, appears to represent the largest known specimen from this family. One new species (Bornella irvingi) from Ducie Atoll is described here for the first time.