In this work, pure and 3% TM (Co, Ni, and Cu)-doped ZnO nanostructures were prepared by microwave-hydrothermal method. The striking similarities between changes in the lattice volume, bandgap energy, morphology and saturation magnetization indicated a strong correlation between these properties. XRD, SAED and HRTEM analyses revealed that all the TM-doped ZnO nano-structures have wurtzite structure and no secondary phase was detected. FESEM and TEM results confirmed a higher aspect ratio and highly crystalline nature of nanostructures. Raman spectra revealed that no defect related mode was observed which indicated that the nanostructures have high quality and negligible defects. The value of bandgap was found to decrease with the increase in atomic number of TM dopants. RTFM was observed in all the TM-doped ZnO nanostructures and the value of Ms and Mr were decreased with TM dopants.