A nanocomposite Cu-TiB₂ powder was synthesized in situ by means of self-propagating high-temperature synthesis (SHS) using high-energy ball-milled Ti-B-Cu elemental mixtures as powder precursors. The effect of the preliminary mechanical treatment on the SHS reaction was studied. The size of the TiB₂ particles produced by SHS decreased upon increasing the duration of the preliminary mechanical treatment. Subsequent mechanical treatment of the SHS products led to a reduction of the sizes of the TiB₂ particles down to 30~50 nm. The microstructural evolution of the synthesized powder compacts during sintering was investigated. During spark plasma sintering, a fine-grained skeleton of TiB₂ with well-connected particles was formed. This interpenetrating phase composite of Cu-TiB₂ is produced by the simultaneous action of pressure, temperature, and electrical current. The TiB₂ nanoparticles distributed in the copper matrix agglomerate to form a fine-grained skeleton. Upon conventional sintering, the nanoparticles show a surprising behavior: at low temperatures, fiber-like structures are formed while higher temperatures caused faceted crystals to be observed.