The interest in synthesising inorganic nanomaterials for biological applications has increased in recent years,especially for antibacterial purposes. In the present study, spherical and cube-shaped copper nanoparticles were synthesised by a chemical reduction method and their efficacy as antimicrobial agents against both Gram-negative(Escherichia coli)and Gram-positive(Enterococcus sp.) organisms investigated. The nanoparticles were characterised using ultraviolet/visible spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. Copper nanocubes were found to be more antimicrobial when compared with copper nanospheres, and it is postulated that whilst both sets of nanoparticles have similar total surface areas, the different shapes have different active facets and surface energies,which may lead to differing bactericidal behaviour. The interest in synthesising inorganic nanomaterials for biological applications has increased in recent years, especially for antibacterial purposes. In the present study, spherical and cube-shaped copper nanoparticles were synthesized by a chemical reduction method and their efficacy as antimicrobial agents against both Gram-negative The bacteria were characterized using ultraviolet / visible spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. Copper nanocubes were found to be more antimicrobial when compared with copper nanospheres, and it is postulated that whilst both both sets of nanoparticles have similar total surface areas, the different shapes have different active facets and surface energies, which may lead to differing bactericidal behavior.