Bulk nanocrystalline 304 stainless steel (nanocrystalline 304ss) discs had been successfully prepared by the commercial microcrystalline 304 stainless steel (microcrystalline 304ss) plate using severe rolling technique. Micro-hardness was measured to reveal the different mechanical behavior after the severe plastic deformation. The electrochemical corrosion resistance and ion release behavior after immersion of the samples were investigated in Hank’s solution for its potential use as implant and orthodontic appliance in body. Furthermore, murine fibroblast cells were indirectly employed to detect cytotoxicity by co-incubation with the extraction from the given materials. Haemocompatibility, consisting of hemolysis test and adhesion of the platelets, was also measured with fresh human whole blood and platelet-rich plasma respectively. Polarization resistance trials indicate that nanocrystalline 304ss is more corrosion resistant in the Hank’s solution, with lower current density and superficial corrosion morphologies. The release values of the biotoxic ions after immersion do not exceed the set limit and turn to be well below the critical value necessary to induce allergy and below daily dietary intake level. Cellular interaction is observed via the proliferated feature of the cell line. Hemolysis and platelet adhesion results elucidates that nanocrystalline 304ss is biological and hematologic compatible.