A new, fast proton-conducting TiO2-P2O5 glass-ceramic was developed and investigated through microstructure observation and electrical conductivity measurements. TiO2-P2O5 glass-ceramic samples were prepared by a sol-gel method and post-annealing heat treatment. With an increase in the post-annealing temperature, growth of TiP2O7 crystals in the TiO2-P2O5 glassy phase was observed. In addition, a tenfold enhancement in maximum conductivity was observed after postannealing heat treatment compared with the as-prepared sample and polycrystalline TiP2O7. The interfacial layer between the TiO2-P2O5 glassy phase and the TiP2O7 crystal phase may act as a fast proton-conducting path, thereby improving the total conductivity. This hypothesis is discussed using the brick layer model.