The ocean supplies a lot of organisms that are beneficial to the life of living things. One of them is cyanobacteria that are widely studied having bioactive compounds. This research was conducted to observe the compounds and the cytotoxic activity toward cancer cells from the Udar Island waters, Sabah, Malaysia. The identity of the sample was completed by using 16S deoxyribonucleic acid (DNA) method and a phylogenetic tree was built to check the similarity of the genus. The compounds from the crude extract were examined by Liquid Chromatography Mass Spectrometry (LCMS) and the cytotoxic activity was examined by 3-(4,5-Dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay. Several known compounds such as Apratoxins and a possible new compound of ethyl acetate fraction were observed and have good cytotoxic activity towards Michigan Cancer Foundation (MCF) 7 breast cancer. The compounds are mainly peptides. The Moorea sp. from Udar Island waters has cytotoxic compounds which exhibits 100% cytotoxicity at concentration of 1 μg/mL. This finding could be the opportunity for the discovery of anticancer compounds.