Synthesis of B4C–TiB2 composite powders via a carbide boronizing process was performed in a pulsed electric current sintering furnace with a specially designed graphite die/punch set-up. Pure B4C–TiB2 powders could be obtained at 1200 °C for 0 min or 1000 °C for 15 min with a total thermal cycle time of only 12–25 min. In the as-prepared B4C–TiB2 composite powders, submicrometer B4C particles were surrounded by nano-TiB2 particles with an average particle of less than 50 nm. The bulk B4C–TiB2 ceramic sintered from the as-prepared composite powders had a relative density of 96% with ultrafine microstructures.