A conductive TiC nanopowder was incorporated into nanosized beta-Si3N4-based powder and consolidated by a spark plasma sintering (SPS) technique with a rapid heating process. The influence of the conductive phase on the microstructure development of the Si3N4 matrix was demonstrated. After sintering, the conductive phase transformed into titanium oxycarbonitride. The Si3N4-based composite containing 5 wt% nano-TiCxOyNz shows a larger average grain size and aspect ratio than the monolithic Si3N4-based ceramic. This is possibly because a leakage current hops across the conductive titanium oxycarbonitride grains and causes Joule heating during sintering. The transmission electron microscopy analysis confirmed that dissolution-reprecipitation and coalescence occur. In addition, although the increasing amount of incorporated nano-TiCxOyNz (10 and 20 wt%) decreases the electrical resistivity of the composites, the pinning effect of the titanium-based phase significantly suppresses the grain growth of Si3N4 matrix grains. beta-Si3N4-based nanocomposites containing nanosized titanium oxycarbonitride were thus obtained in the present study.