The spatial distribution and atomic mobility of Li ions in the solid solution system Li1-xNb1-xWxO3 (0 ≤ x ≤ 0.5) have been studied using solid-state NMR techniques. To maintain charge balance, for each tungsten atom substituting on a niobium site, a lithium vacancy is produced in the lithium sublattice. 6Li magic angle spinning experiments reveal multiple lithium sites, attributed to distributions of niobium and tungsten neighbors. Dipolar 7Li second moments measured at low temperature (−100 °C) depend linearly on lithium content, consistent with a random distribution of vacancies. Variable temperature (−20 to 550 °C) 7Li NMR studies as a function of composition give evidence for two distinct motional processes: at low temperatures (near 0 °C) a local hopping process involving only a minority of the lithium ions present is activated. At high temperatures (300 °C and above, depending on substitution levels) long-range diffusion involving all the lithium atoms is evident on the NMR time scale. As the substitution level x is increased, the long-range mobility of lithium increases. In contrast, the number of lithium atoms participating in the low-temperature process and their respective mobilities reach a maximum near x = 0.25. This result is explained on the basis of detailed simulations, considering favorable cation transport mechanisms through intrinsic vacancies of the LiNbO3 lattice. Both the 6Li line shape and the 7Li dynamics simulations are consistent with a statistical distribution of Nb and W atoms and formation of W-vacancy pairs along the c-axis.