This study aims to assess the cytotoxic activity against MCF-7 breast cancer cells and the content of secondary metabolites from the hexane extracts of Gracilariasaliconia. Samples of G. salicornia were taken from Hari Island waters, Southeast Sulawesi, Indonesia, and then extracted by maceration using hexane. Chemical content was analyzed using phytochemical tests and Gas Chromatography-Mass Spectrometry (GCMS). Toxicity potential was evaluated using the Brine Shrimp Lethality Test (BSLT) method, and cytotoxicity to MCF-7 cells using the MTT method (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide). This study showed that the hexane extract showed a cytotoxic potential of 248.40 mg/L (BSLT) and 325.34 mg/L (MTT). This activity was supported by the phytochemical screening of hexane extracts containing alkaloid, phenolic, and steroid/terpenoid compounds. GCMS data of hexane extract contains 16 secondary metabolites with the main compounds 1-(1-(Methylthio) propyl)-2-propyldisulfane; N-Methoxydiacetamide; Hydrazine, 1,1-dimethyl-2-propyl. This study concludes that the hexane extracts from G. salicornia contain many secondary metabolites, which may be responsible for the cytotoxic activity against MCF-7 breast cancer cells.