Dense YB22C2N samples were directly synthesized from powder mixtures via reactive spark plasma sintering. The gas/solid reaction step was applied to introduce nitrogen into the mixture during heating. The sample reactively sintered at 1700 °C for 10 min after the gas/solid reaction step at 1200 °C for 30 min consisted of YB22C2N with small amounts of secondary phases. The thermoelectric behavior shifted toward n-type behavior with increasing amount of YB22C2N phase. This newly developed synthesis technique could facilitate the rapid and cost-effective preparation of complex borocarbonitrides.