This study reports the in vitro antimicrobial and anticancer activities of biologically synthesized copper nanoparticles. The antimicrobial activity of green synthesized copper oxide nanoparticles was assessed by well diffusion method. The anticancer activity of brown algae-mediated copper oxide nanoparticles was determined by MTT assay against the cell line (MCF-7). Maximum activity was observed with Pseudomonas aeruginosa and Aspergillus niger. Effective growth inhibition of cells was observed to be more than 93% in antibacterial activity. Thus, the results of the present study indicates that biologically synthesized copper nanoparticles can be used for several diseases, however, it necessitates clinical studies to ascertain their potential as antimicrobial and anticancer agents.