In this study, we report that the carrier mobility of 2%-La-doped BaSnO 3 (LBSO) films on (001) SrTiO 3 and (001) MgO substrates strongly depends on the thickness whereas it is unrelated to the film/substrate lattice mismatch (+5.4 % for SrTiO 3 , −2.3 % for MgO). The films exhibited large differences in the lattice parameters, the lateral grain sizes (~85 nm for SrTiO 3 , ~20 nm for MgO), the surface morphologies, the threading dislocation densities, and the misfit dislocation densities. However, the mobility dependences on the film thickness in both cases were almost the same, saturating at ~100 cm 2 V −1 s −1 while the charge carrier densities approached the nominal carrier concentration (=[2 % La 3+ ]). Our study clearly indicates that the carrier mobility in LBSO films strongly depends on the thickness. These results would be beneficial for understanding the carrier transport properties and fruitful to further enhance the mobility of LBSO films.program funded from following programs of each country: International