Objective: The present study aims to isolate and characterize dioxolo-pyran derivative from marine green algae, Codium elongatum. Method: The dioxolo-pyran derivative (DOPD) was isolated by aqueous extraction and purified by ethanol precipitation. The structure of DOPD was established with the help of infrared spectroscopy, nuclear mass spectroscopy and mass spectroscopy. An acute toxicity study of water extract and isolated DOPD was also conducted for the first time according to OECD (Organization for Economic Co-operation and Development) 423 guidelines. Results: DOPD having IUPAC name: (3aR,5R,5aS,8aS,8bR)-5-((((2S,5S,6R)-5-(benzyloxy)-6-((benzyloxy)methyl)-5,6-dihydro-2H-pyran-2-yl)oxy)methyl)-2,2,7,7-tetramethyltetrahydro-5 H-bis ([1,3]dioxolo)[4,5- b:4',5'-d]pyran and chemical formula: C32H40O9 has been isolated from C.elongatum. The findings were further supported by the results of IR, ESI-MS, 1H-NMR and 13C-NMR. Acute toxicity studies of DOPD and water extract showed no significant effect at the dose of 300 mg/kg and 2000. mg/kg.