The grain-growth kinetics of fully dense MgO compacts containing various amounts of CaMgSiO4 from 1 to 20 wt% was investigated. The relationship between grain size, volume fraction of liquid phase, and annealing time was determined. The exponent of grain growth (n) was 3, independent of the volume fraction of the liquid phase, and the rate constant (k) was inversely proportional to the volume of liquid. The overall grain-growth kinetics was governed by mass transport through liquid pockets at grain corners, which provided the longest diffusion paths between the grains. This result was modeled after a solid-state system containing isolated pores in which the pores move by vapor-phase diffusion.