Ti-Al diffusion couples, prepared by resistance spot welding, were annealed up to 112 hours at 823, 848, and 873 K in ambient atmosphere. The interfacial microstructure was observed and analyzed using SEM and TEM. The growth characterization of intermetallic compound formed at the Ti/Al solid state interface was investigated. Only TiAl₃ phase was detected in the interfacial zone, and its growth was governed by reaction-controlled mechanism in the previous period and by diffusion-controlled mechanism in the latter period. The activation energies were 198019 and 122770 J/mol for reaction-controlled and diffusion-controlled mechanism, respectively.