OBJECTIVE: To extract the bioactive compound from Enteromorpha intestinalis (E. intestinalis) and determine its in vitro antimicrobial activity. METHODS: E. intestinalis was extracted by methanol and subjected to antimicrobial screening. The antimicrobial activity was studied by using disc diffusion and broth dilution method. The effect of the extract on the growth profile of the bacterial was also examined via time-kill assay. Microscopy observations using SEM was done to determine the major alterations in the microstructure of methicillin-resistant Staphylococcus aureus (MRSA). RESULTS: The results showed methanolic extract of E. intestinalis exhibited a favourable antimicrobial activity against tested bacteria with produced inhibition zone ranging from 8.0 to 19.0 mm. However, all the tested fungi and yeast were resistant to the extract treatment. Time kill assay suggested that methanolic extract of E. intestinalis had completely inhibited MRSA growth and also exhibited prolonged antibacterial activity. The main abnormalities noted from the microscopic observations were the structural deterioration in the normal morphology and complete collapsed of the bacteria cells after 36 h of treatment. CONCLUSIONS: The significant antibacterial activity shown by crude extract suggested its potential against MRSA infection. The extract may have potential to develop as antibacterial agent in pharmaceutical use.