Crystals of LiKGdF5∶Er3+, Tb3+ grown by the hydrothermal synthesis technique with concentrations of 2% and 0.4% were analysed. By using site selective excitation measured at low temperature, luminescence and excitation spectra from Er3+ and Tb3+ ions embedded in LiKGdF5 were clearly separated. The lifetimes of the emitting levels 4S3/2 of Er3+ and 5D4 of Tb3+ were also determined. Following the site selective spectroscopy study, the dominant energy transfer process from Tb3+ to Er3+ in the crystal was then investigated via transient experiments.