Ultra-high temperature ceramic (UHTC) hybrid powders modified using in situ grown SiC nanowires (SiCNWs) were successfully prepared via a simple catalytic method. The self-produce carbon and silicon source promoted the growth of SiCNWs during the pyrolysis process of ZrB2 polymer precursors coated ZrB2-SiC powders. The results showed that the growth of SiCNWs could be explained by a tip-growth model and vapor–liquid–solid (VLS) growth mechanism. The SiCNWs with diameter of 200 nm were single crystalline, and the content could be controlled by changing the catalyst content.