Improved bone bonding ability and antibacterial activity are two critical requirements for implants. In this work, novel dual surface modifications of dealloying and polydopamine/silver coating on a NiTi alloy were conducted. Scanning electron microscopy (SEM) results show a porous layer with interconnected micro- and nano-pores on the dealloyed NiTi alloy. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) results confirm the formation of a polydopamine/silver coating on the surface of the dealloyed NiTi alloy. The silver nanoparticles (58.9 nm, in the polydopamine/silver coating) on the dealloyed NiTi alloy surface are smaller when compared with pristine NiTi alloy (73.1 nm). Moreover, the dealloyed NiTi alloy with polydopamine/silver coating exhibits better antibacterial activity against Escherichia coli (99.7%) and Staphylococcus aureus (99.4%) than pristine NiTi alloy with the same coating (97.3% and 96.5%, respectively), due to the larger surface area, higher silver content, and smaller silver nanoparticles that trigger more silver ion release. The combined dealloying and coating method is an effective way of increasing antibacterial activity of NiTi alloys. The findings presented in this work may provide a new guidance for the surface modification of NiTi implant materials.