Ti3SiC2 is synthesized by self-propagating high-temperature synthesis (SHS) of elemental titanium, silicon, and graphite powders. The reaction paths and structure evolution are studied in situ during the SHS of the 3Ti+Si+2C mixture by time-resolved X-ray diffraction coupled with infrared thermography. The proposed reaction mechanism suggests that Ti3SiC2 might be formed from Ti-Si liquid phase and solid TiCx. Finally, the effect of the powders starting composition on the Ti3SiC2 synthesis is studied. For the investigated initial mixtures, TiCx is always formed as a major impurity together with the Ti3SiC2 phase.