Titanium plates with a Ti−O solid solution surface-hardened layer were cold roll-bonded with 304 stainless steel plates with high work hardening rates. The evolution and mechanisms affecting the interfacial bonding strength in titanium/stainless steel laminated composites were investigated. Results indicate that the hardened layer reduces the interfacial bonding strength from over 261 MPa to less than 204 MPa. During the cold roll-bonding process, the hardened layer fractures, leading to the formation of multi-scale cracks that are difficult for the stainless steel to fill. This not only hinders the development of an interlocking interface but also leads to the presence of numerous microcracks and hardened blocks along the nearly straight interface, consequently weakening the interfacial bonding strength. In metals with high work hardening rates, the conventional approach of enhancing interface interlocking and improving interfacial bonding strength by using a surface-hardened layer becomes less effective.