Phytochemical investigation of Sargassum fusiforme (Harv.) Setch. lead to the discovery of fifteen small-molecular-weight compounds, including three sterols (1-3), three monoterpenes (4-6), five nitrogenous compounds (7-11), two fatty acids (12 and 13), and two others (14 and 15). Among them, compounds 1 and 2 are new compounds, while compounds 3-15 were isolated from S. fusiforme for the first time. The structures of 1 and 2 were identified by NMR and HRESIMS data analyses, and the absolute configurations were established by comparing the calculated and experimental ECD spectroscopic data.