Green synthesis of copper oxide NPs was done using an environment friendly and low cost method with aqueous extract of stem of Cuscuta reflexa which acted as an efficient reducing agent in the formation of CuONPs. The color of the colloidal solution changed from blue to brown indicating the synthesis of NPs. TEM and SEM study showed that the particles were mostly spherical in size with average particle size of 35 nm. DLS characterization revealed that the hydrodynamic radius of CuONPs was 103 nm with -14 mV as zeta potential. FTIR confirmed various phytochemical responsible for stabilization of CuONPs. Disc diffusion method was used to determine the antibacterial activity of CuONPs which showed significant inhibitory activity against pathogenic bacteria S.aureus and E.coli. The NPs also revealed anticancer activity against MCF-7 cell line.