Melastoma decemfidum (M. decemfidum) or locally identified as “senduduk putih” is a small shrub with white petals. Locally, different part of M. decemfidum has been used as traditional remedies for various illnesses. It is used to treat postpartum conditions, hepatitis, leucorrhea, swelling, mouth ulcer, toothaches, and sinusitis. The objective of this study is to determine the antibacterial activities of methanolic extract of different parts of M. decemfidum which includes flower, leaves and stem. These extracts of M. decemfidum was used to study the antibacterial activity against two Gram positive bacteria (Bacillus cereus, Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa) by disc diffusion method at different concentrations (100, 150, 200, 250 mg/ml). The antibacterial activity is determined from the evaluation of the zone of inhibition. Based on the results, the different parts of M. decemfidum exhibited diverse activity against the tested bacteria. The largest diameter of zone of inhibition was 22.6 mm which was recorded by stem extract (250 μg/mL) against Pseudomonas aeruginosa. The maximum diameter of zone of inhibition recorded by flower and leave extract were both 15.8 mm against P. aeruginosa at 250 μg/mL. The antibacterial activities shown by M. decemfidum could indicates its potential for development of new drugs for pharmaceutical application.