The focus of this work is to study the effect of cobalt (Co) and Mg doping on structural, surface morphological, photocatalytic, antibacterial and magnetic properties of ZnO nanopowders. The undoped and doped ZnO nanopowders were prepared using a simple, speedy and cost-effective microwave assisted synthesis. The XRD studies reveal that the Co doping only slightly degrade the crystalline quality of ZnO nanopowder whereas Mg doping causes a considerable degradation in the crystallinity. This result is interpreted on the basis of lattice compatibility theory. Surface morphological study shows that ZnO nanopowder exhibits hexagonal shaped grains. The Co doping results in well defined needle and disc shaped grains while spherical shaped ZnO nanopowders are observed for Mg doped ZnO nanopowders. The EDAX spectra affirm the presence of anticipated elements Zn, O, Co and Mg. The Co doping induces room temperature ferromagnetism in ZnO nanopowders. Both the dopants enhance the photocatalytic activity against methylene blue dye and antibacterial activities against gram negative bacteria such as E. coli and Vibrio cholerae. Between the Co and Mg doped ZnO nanopowders, the former seems to be superior in photocatalytic and antibacterial activities.