A solid-state diffusion technique has been performed to study systematically the diffusion kinetics of Ti–Zn binary system in the temperature range of 573–648 K. The number of detected product phases in the diffusion region increases with increasing annealing temperature from one (Ti3Zn22) to four (TiZn3, TiZn5, Ti3Zn22, and TiZn16) intermetallic compounds (IMCs). The integrand diffusion coefficients and activation energies of the four IMCs were estimated based on the quantitative distribution of elements examined by electron probe micro-analyzer (EPMA). TiZn16 has the largest diffusion activation energy. The mechanical properties of the four IMCs were investigated by using nanoindentation characterization technology and first-principles calculations. The nanoindentation tests show that the hardness of TiZn3, TiZn5, Ti3Zn22, and TiZn16 are 5.37, 5.86, 5.67 and 2.93 GPa, respectively. The experimental result of Young's modulus of the detected IMCs increases with the increase of Zn content, while the results of first-principles calculations increase firstly and then decrease. The obtained kinetic and mechanical information should be conducive to the development of Ti–Zn alloy.