Aims: The specific aim of this study was to evaluate for the first time the phytochemical constituents, functional group assignment, and antibacterial activities of the Philippine green-leafed Acalypha amentacea Roxb. (Maslakot-Ambulong), a wildcrafted medicinal plant of local traditional healers in the southern most region of Mindoro province. Methodology and results: Aqueous leaf extracts of A. amentacea Roxb. were lyophilized and subjected to qualitative phytochemical screening and FT-IR analysis. The antibacterial activity of the plant using agar-well diffusion assay revealed highest Zone of Inhibition (ZOI) in 500 mg/mL concentration for Staphylococcus aureus (21.78 mm), Escherichia coli, (21.36 mm), Serratia marcescens (21.90 mm), Klebsiella pneumoniae (21.44 mm), and Enterococcus faecalis (20.52 mm) among other concentrations suggesting a dose dependent bioactivity. Also, compared to the antibiotic Rifampicin, A. amentacea Roxb. demonstrated better bioactivity against all the selected bacteria except S. aureus (p<0.05) and comparable to Ofloxacin when against E. faecalis. The minimum inhibitory concentration (MIC) of the extract was found to be at 15.6 mg/mL for all the bacteria except for S. marcescens with 31.25 mg/mL as MIC. The bioactivity of the plant may be accounted to the presence of alkaloid, phenol, flavonoid, tannin, and saponin which were supported by its functional groups like carboxylic acid, alcohols, amine, conjugated alkene, aromatic esters, and alkyl aryl ether. Conclusion, significance and impact of study The results of this investigation, proved that A. amentacea Roxb. has bioactive antibacterial principles against the selected microorganisms. This also confirms its potentiality as a new source of antibacterial agents.