The present paper deals with the ecology and population characteristics of the sipunculid Apionsoma (A.) misakianum from the Aegean Sea, which is a new record for the Mediterranean Sea. A total of 571 specimens of this species were collected at 25 stations between 41 and 195 m depth. The majority of specimens were found between the depth intervals 101-150 m (46%) and 151-200 m (45.2%). The biometrical parameters such as the trunk length and individual wet weight of the specimens were evaluated using regression and correlation analyses. In addition, the morphological, ecological and distributional features of the species are given and discussed.