Lithium-ion dynamics of garnet-type Li${}_{6.5}$La${}_3$Zr${}_{1.5}$Ta${}_{0.5}$O${}_{12}$ single crystals were investigated using pulsed field gradient (PFG) NMR and impedance spectroscopy over a wide temperature range up to 700 K. The diffusion coefficient measured by PFG-NMR exhibits non-Arrhenius behavior at elevated temperatures (>400 K). The conductivity diffusion coefficient is consistently higher than the PFG-NMR diffusion coefficient across the entire temperature range, with a Haven ratio of 0.3–0.4, indicating that the motion of mobile Li${}^{+}$ ions is correlated. Remarkably, the Haven ratio exhibits little temperature dependence despite the non-Arrhenius behavior, representing the first experimental observation in garnet-type electrolytes and consistent with the molecular dynamics simulations. This indicates that ion–ion correlations remain essentially unchanged over a wide temperature range. Combined with the local Li${}^{+}$ ion dynamics obtained from spin-lattice relaxation analysis, these results suggest that long-range diffusion is suppressed at low temperatures due to short-range ordering of Li${}^{+}$ ions.