The effects of Na-citrate on the morphology change of ZnO films, grown on ZnO buffered glass substrates by hydrothermal synthesis at 90 degrees C and at pH 10.9, have been investigated. Dense and smooth ZnO film consists of ZnO nano-rods that have flat ends was grown with Na citrate. However, very rough ZnO film consists of ZnO nano-rods that have sharp ends were grown without Na citrate. X-ray diffraction analysis shows that all the ZnO films were grown with strong c-axis out-of-plane orientation. Optical transmission spectroscopy of the ZnO films grown with and without Na-citrate shows band gap energy values of 3.36 eV and 3.28 eV, respectively. Photoluminescence results showed strong defect related emission peak centered near 545 nm in the ZnO film grown without Na citrate and strong band-edge emission peak centered near 378 nm in the ZnO film grown with Na citrate.