The thermal and electrical properties of MoSi2 and/or SiC-containing ZrB2-based composites and the effects of MoSi2 and SiC contents were examined in hot-pressed ZrB2-MoSi2-SiC composites. The thermal conductivity and electrical conductivity of the ZrB2-MoSi2-SiC composites were measured at room temperature by a nanoflash technique and a current-voltage method, respectively. The results indicate that the thermal and electrical conductivities of ZrB2-MoSi2-SiC composites are dependent on the amount of MoSi2 and SiC. The thermal conductivities observed for all of the compositions were more than 75 W.(m.K)(-1). A maximum conductivity of 97.55 W.(m.K)(-1) was measured for the 20 vol% MoSi2-30 vol% SiC-containing ZrB2 composite. On the other hand, the electrical conductivities observed for all of the compositions were in the range from 4.07 x 10-8.11 x 10 Omega(-1).cm(-1).