Alstonia angustifolia were applied in traditional medicine to cure malaria disease and remittent fever. The aim of this study is to evaluate the potential antibacterial properties of A. angustifolia leaf extract under in vitro condition. The leaf extract was tested on various Gram-positive and Gram-negative bacteria to evaluate the inhibition pattern using disc diffusion assay, minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) technique. Disk diffusion assay showed that S. aureus, S. epidermidis, S. saprophyticus, B. cereus and B. subtilis were susceptible to the extract while K. pneumonia, P. aeruginosa, S. typhi, A. baumannii and E. coli were resistant. The lowest MIC values were 6.25 mg/ml, 12.5 mg/ml for S. aureus and B. subtilis respectively, at 24 h and 48 h of incubation period. The MBC value for S. aureus, B. subtilis and B. cereus showed no different, within 24 h and 48 h, however the other values had raised. The plant has potential to be commercialized in pharmaceutical and other industries.