Dissimilar friction stir welding was conducted on the combination of pure Ti and carbon fibre reinforced plastic. The weld interface microstructure and mechanical properties of the obtained joints were systematically investigated. Before welding, a surface treatment was performed on the Ti surface using a silane coupling agent. As a result, the silane coupling agent treatment helped to fabricate the sound dissimilar Ti/CFRP joint. The dissimilar Ti/CFRP joints obtained at the interface temperature between the melting point of the CFRP and thermal decomposition point of the CFRP showed superior tensile-shear strength due to the formation of the sufficient reaction between the surface-modified Ti and CFRP and the suppression of welding defect formation in the CFRP near the weld interface.