In this study we report the facile synthesis of environmentally benignant copper nanoparticles (CuNPs) using Cuminum cyminum (Cumin) seed extract. Bio-molecules present in the seed extracts can be used to reduce the metal ions to nanoparticles in a single-step green synthesis process. The synthesized CuNPs have been characterized by studying the structural, morphological, optical and antimicrobial properties. The x-ray diffraction (XRD) pattern was used to analyze the phase and crystal structure of the nanoparticles formed. The morphology and shape of CuNPs were studied by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. The existence of elemental copper (Cu) was revealed by energy dispersive spectroscopy (EDS) analysis. The presence of an absorption peak at 590 nm using ultraviolet-visible (UV-Vis) spectroscopy confirms the formation of CuNPs. Fourier transform infrared spectroscopy (FTIR) spectrum ascertains the reduction and capping nature of phytoconstituents of seed extract in CuNPs synthesis. Antimicrobial activity of CuNPs showed the better inhibitory activity towards Pseudomonas spp. and Penicillium spp. compared to other test pathogens through the standard Kirby-Bauer's disc-diffusion method. © 2018 Vietnam Academy of Science & Technology.