Highly luminescent and weak ferromagnetic ZnO nanorods were prepared by a facile solvothermal method. Luminescence studies carried out on as-synthesized ZnO nanorods, subjected to heat treatment in a variety of environments, established that Zn vacancies are responsible for the green emission. A significant change in morphology has been found on treating these as-synthesized nanorods in hydrogen, even at room temperature, which is attributed to the removal of oxygen from the already Zn-deficient ZnO lattice.