Carbon fiber reinforced carbon composites (CFRC) thermo-structural composites are applied as aerospace devices. This work aims to process and characterize CRFC composites modified by ZrB2 and ZrC particles. ZrB2 is a ultra-high temperature ceramic.  Four composites were processed using novolac phenolic resin (NR), carbon fibers (C_f), ZrB2 and ZrC at the proportions of 40%NR/60%Cf, 40%NR/30% ZrB2/30%C_f, 40%NR/30% ZrC/30%C_f and 40%NR/15% ZrB2-15% ZrC/30%C_f. Twelve layers of carbon fiber fabrics were stacked and interleaved with the mixture of resin and powder. Subsequently, composites were cured under pressure in a vacuum bag up to 180 °C, followed by heat treatment at 1000 °C and at 1800 °C. Composites were characterized by density, microstructure and crystalline phases. Delamination was not observed in the composites after cure and thermal treatments. Distribution of ZrB2 and ZrC particles in the matrix was homogeneous. ZrO2 was identified after heat treatment at 1000 °C and ZrC after 1800 °C in composites with ZrB2 addition. The powder addition improved considerably the composites oxidation resistance.