Three hot-pressed ZrB2-based ultra-high-temperature ceramic composites (UHTCC), ZrB2–SiCp (ZS), ZrB2–SiCp–C (ZSC), and ZrB2–SCS9A (SiC fiber)–SiCp (ZSS), were joined to Cu–clad–Mo using AgCuTi brazes (TL∼1073–1173K) and Pd-base brazes (TL∼1493–1513K). More extensive chemical interactions occurred in Pd-base joints than in AgCuTi-base joints. The Pd-braze region displayed higher hardness in joints made using ZS than ZSS and ZSC. Residual stress calculations point toward negative strain energy up to ∼23% clad layer thickness because αCu–clad–Mo<αZS (α=coefficients of thermal expansion). Above this thickness, αCu–clad–Mo>αZS, strain energy is positive, and it increases with increasing thickness. Projected reductions in the thermal resistance highlight the benefits of joining the UHTCC to Cu–clad–Mo.