In this work, effects of annealing temperature of seeding layer on structural properties and morphologies of Ga/F co-doped ZnO nanostructures synthesized by hydrothermal process were investigated by varying the annealing temperature of seed layer as 300-500 °C. The ZnO seeding layers were deposited onto cleaned glass substrates by dip-coating technique using zinc acetate dehydrate (CH3COO)2Zn·2H2O as starting coating precursor. The Ga/F co-doped ZnO nanostructures were then grown on these seed layers by conventional hydrothermal process using Zn(NO3)2, NH4F, GaN3O9 and hexamethyltetramine as Zn, F and Ga sources, respectively. Effect of seed layer annealing temperature on morphologies, structural and Photoluminescence properties was investigated by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), and Photoluminescence spectra, respectively. Variation of annealing temperature of seed layers can significantly result to the difference in morphological, structure and shape of the as-synthesized nanostructure products. It is found that the increase in annealing temperature leads to alternation in their shape from vertically-aligned nanosheets to nanorods with their average size ranging from 50 to 200 nm. Furthermore, the luminescence could be ascribed to the different contributions of the defect emissions, such asthe increase in the oxygen vacancy (VO) emissionor the decrease of the Zinc vacancy (Vzn). However, it can be speculated from the photoluminescence that the incorporated Ga and F substitute into ZnO.