Artículo de publicación ISIGreen synthesis of hierarchical copper oxide (CuO) microleaf bundles was performed using Hibiscus cannabinus (H. cannabinus) leaf extract and characterized through X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectrometer. XRD pattern of CuO disclosed diffraction peaks correspond to monoclinic crystal structured CuO. SEM images revealed formation of hierarchical CuO microleaf bundles and TEM images demonstrated presence of randomly distributed CuO microleaves that are built up of several small CuO nanoparticles. EDAX spectrum showed peaks analogous to Cu and O elements that confirm the purity of hierarchical CuO microleaf bundles. High performance liquid chromatography (HPLC) analysis of H. cannabinus leaf extract revealed the presence of gallic acid as a chief phytochemical could act both as a reducing and stabilizing agent during synthesis process. Antibacterial potential of the hierarchical CuO microleaf bundles against selected Gram-positive and Gram-negative strains were assessed through well diffusion and broth microdilution methods. Probable mechanisms for the better antibacterial activity of hierarchical CuO microleaf bundles against Gram-positive strains are discussed.