The study aims to prepare reliable, ecofriendly and cost efficient zinc nanoparticles (Zn NPs) by Mentha piperita L. leaf extract and zinc sulfate heptahydrate, for four pathogenic bacteria. Synthesized NPs were investigated by using X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Zeta Potential. Disc diffusion method was used to check their antibacterial activity. For synthesizing Zn NPs leaf extract was used as a biological reducing agent. During reaction, appearance of cloudy white solution due to reduction in the number of zinc ions, indicated the Zn NPs formation. XRD determined the average NPs size i.e. 9.8 nm. FTIR confirmed the presence of functional groups in the leaf extract sample. Spherical shape of the NPs was confirmed by the SEM analysis. Antibacterial activity of the Zn NPs was measured by the inhibition zones against various bacteria (E. coli, P. aeruginosa, S. aureus and S. pneumoniae). Inhibition zones were observed in the range of 2.9 to 12.9 mm.