In this investigation, TiB₂–TiC composite powders, synthesized via the boron/carbon thermal reduction process, were employed as precursor materials. SiC, serving as the tertiary constituent, was incorporated to fabricate TiB₂–TiC–SiC composite ceramics utilizing spark plasma sintering technology. The present study initially elucidates the densification mechanisms and investigates the influence of sintering temperature on the densification behavior, microstructural evolution, and mechanical properties of the resultant ceramics. The experimental findings reveal that the sintering process of TiB₂–TiC–SiC ceramics exhibits characteristics consistent with solid-phase sintering. As the sintering temperature escalates, both the relative density and mechanical properties of the ceramics initially improve, reaching a maximum at an optimal sintering temperature of 1900 °C, before subsequently declining. Microstructural examinations conducted at this optimal temperature indicate a homogeneous distribution of the two primary phases, with no evidence of excessive grain growth. Furthermore, this research explores the effects of SiC addition on the mechanical performance and oxidation resistance of TiB₂–TiC–SiC composite ceramics. The results demonstrate that the incorporation of SiC effectively suppresses grain growth and promotes the formation of rod-like TiB₂ microstructures, thereby enhancing the mechanical attributes of the ceramics. Additionally, the addition of SiC significantly improves the oxidation resistance of the composite ceramics compared to their TiB₂–TiC binary counterparts