Abstract: Annona muricata (soursop) leaf have been widely known for its ethnomedicinal uses, anti-cancer, anti-microbial and antioxidant activities. Previous studies reported that A. muricata have the potential to exhibit anti-cancer, antimicrobial and antioxidant activities. However, there are very few studies of A. muricata from Sarawak. These phytochemical and biological studies were aimed to determine the chemical constituents, total flavonoid content, total phenolic content, antioxidant, antimicrobial and anticancer activities. The leaf of Annona muricata was extracted using 95% ethanol and yield 13.03% crude extract. The compound was obtained through isolation and purification by using various chromatographic methods such as radial chromatography and Thin Layer Chromatography (TLC) while the structure was elucidated based on the spectral data such as Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared (FT-IR) and Gas Chromatography-Mass Spectroscopy (GC-MS). The Total Phenolic Content (TPC) and Total Flavonoid Content (TFC) were determined using Folin-Ciocalteu and aluminium chloride methods, respectively. TPC in the ethanolic extract was 195.05 mg GAE/g while the TFC was 64.25 mg QE/g. The antioxidant activity of ethanolic extract which performed using DPPH (2, 2-Diphenyl-1-Pycryl-Hydrazayl) assay has recorded IC50 of 21.03 μg/mL. The antiproliferation activity of this extract against three cancer cell lines, namely breast cancer (MCF-7), cervical cancer (HeLa) and liver cancer (HepG2) was determined using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl- tetrazolium bromide (MTT) assay. The ethanolic leaf extract was found to be selectively cytotoxic in vitro to HeLa, MCF-7 and HepG2 cell lines with IC50 values of 1.4111, 1.7382 and 2.7767 mg/mL, respectively. For the antimicrobial activities, the crude was examined on four bacteria named Staphylococcus aureus (SA), Streptococcus pyogenes (SP), Escherichia coli (EC), Pseudomonas aeruginosa (PA) using MIC and MBC. The extract also showed strong antimicrobial activities with MIC and MBC values of 450 μg/mL. As such Annona muricata may have excellent potential for further development for an antioxidant as well as an alternative antibacterial agent.