Five compounds, including thyrsiferol (1), 11-hydroxy-8-oxo-β-cyperon (2), (+)-elatol (3), [3(15)E,4Z,6S,9S,10R]-10,15-dibromochamigra-3(15),4,7(14)-trien-9-ol (4), and pacifidiene (5) were isolated from the methanol extract of the sea hare Aplysia dactylomela, collected at Quang Ngai province, Vietnam. Their structures were elucidated from HR-ESI-MS and NMR spectral data. Compound 2 was obtained for the first time from A. dactylomela, and its complete NMR spectral data were reported here. All i