Silicon nitride-silicon carbide nanocomposite has been prepared by an in situ method that utilizes C+SiO2 carbo-thermal reduction during the sintering process. The developed material is nearly defect free and consists of a silicon nitride matrix with an average grain size of approximately 200 nm with inter- and intra-granular SiC particles with sizes of approximately 150 and 40 nm, respectively. The creep behavior was investigated in bending at temperatures from 1200 degrees to 1450 degrees C, under stresses ranking from 50 to 150 MPa in air. The stress exponents are in the interval from 0.8 to 1.28 and the apparent activation energy is 480 kJ/mol. A significantly enhanced creep resistance was achieved by the incorporation of SiC nanoparticles into the matrix. This is because of a change of the microstructure and grain boundary chemistry leading to a change of creep mechanism and creep rate.