We have observed room temperature ferromagnetism in In2O3 thin films doped with either 5 at.% Mn or Fe, prepared by pulsed laser deposition at substrate temperatures ranging from 300 to 600 °C. The dependence of saturation magnetization on grain size was investigated for both types of In2O3 films. It is revealed that, for the Mn-doped films, the magnetization was largest with small grains, indicating the importance of grain boundaries. In contrast, for Fe-doped films, the largest magnetization was observed with large grains.