Abstract: Rare earth ions (Ln3+) doped optical materials manifest sharp and tunable emission, high photostability, long luminescent lifetime and low cytotoxicity, and find diverse applications in optics, optoelectronic devices and bio-labelling. Herein, we employed a conventional hydrothermal approach to control the size and tune the phase as well as the morphology of GdF3:Tb3+,Yb3+ nanocrystals, wherein the effects of the synthetic conditions, such as pH, time, the ratio of the Gd to F and the surfactant, have been detailed investigated, producing sphere, platelet, rice, flower-shaped GdF3 nanoparticles. Diffuse reflectance spectra, photoluminescence emission and excitation spectra, and photoluminescence lifetime measurements were employed to characterize the optical spectroscopic properties of GdF3:Tb3+,Yb3+ nanocrystals. No efficient energy transfer from Tb3+ to Yb3+ is observed in GdF3:Tb3+,Yb3+ nanocrystals and the Yb3+ shows a concentration quenching effect at high doping levels. [Copyright &y& Elsevier]