Reactive hot pressing was used to prepare Zr1-xTixB2-ZrC composites with advantageous microstructure and mechanical properties from ZrB2-TiC powders. The reaction mechanisms and the effects of different levels of TiC on the physical and mechanical properties of the resulting composite were explored in detail and compared to conventionally hot-pressed ZrB2 and ZrB2-ZrC. Incorporation of 10 to 30vol% TiC enabled full densification and restrained grain growth, reducing the final average grain size from 5.6m in pure ZrB2 to a minimum of 1.4m in samples with 30vol% TiC. The flexural strengths and hardnesses of the composites sintered with TiC were consequently greater than the conventionally processed ZrB2-ZrC materials, increasing from 440MPa and 17.4GPa to a maximum of 670MPa and 24.2GPa at 10vol% TiC. However, despite a decrease in the total average grain size, the flexural strength at higher TiC levels was limited by an increase in ZrC grain growth, which was observed to determine the flexural strength of the reaction sintered composites similar to the case of ZrB2-SiC.