The present study aims to understand the influence of surface mechanical attrition treatment (SMAT) on corrosion, wear, and in vitro cell viability of Ti-6Al-4V alloy. XRD analysis quantified the extent of surface nanocrystallization and the induced strain, which increased from 0.096 ± 0.021 to 0.166 ± 0.039, and so did dislocation density (from 1.55 × 1022 to 4.62 × 1022). TEM analysis advocated for grain refinement and also manifested the occurrence of mechanical twins as well as dislocation walls in the SMATed surface. SMAT processing decreased the corrosion rate in simulated body fluid by ~75%, from 0.167 ± 0.097 mpy to 0.040 ± 0.015 mpy. This was attributed to the nanocrystallization that led to the creation of a stable and insoluble TiO2 passive film at the interface of the surface and electrolyte. Grain refinement of the SMATed surface also derived an improvement in the wear resistance and cell adhesion property.