Sperm whale residency and movements within the Mediterranean Sea were investigated using photo-identification data collected in summer over a 15 year period (1991–2005). Surveys were conducted from a 12 m motor sailing boat. Although dedicated to cetaceans, surveys did not solely focus on sperm whale photo-identification, so time to track and photograph all individuals forming a group was not always available. From good quality photographs, 44 individuals were identified in the western Mediterranean, including the Ligurian Sea, the Gulf of Lions and waters off the Balearics. Eleven identified whales were photographically re-captures. Within-year re-sightings occurred from 1 to 29 d apart, while five identified whales were re-sighted over several summer seasons, from 1 to 7 y apart. Four whales were seen in more than one year in the northern part of the basin, indicating site fidelity to this feeding area. The combination of photo-identification and acoustic data (size estimation from inter-pulse interval measurements) enabled us to demonstrate a north–south movement of some sexually mature males (around 13 m in length), feeding in the northern regions and joining groups of females off the Balearics for around 20 d. These displacements ranged over ~500 km, with travelling time of seven days or less.