In this work, the spark plasma sintering (SPS) of stainless steel 316L with ultrafine grains was investigated. Ball-milled 316L powder was employed and the process parameters (time, temperature, pressure) were varied over wide ranges to analyze their effect on the microstructure and density of sintered specimens. Using suitable sets of parameters, samples with large densities and homogeneous grain sizes ranging between 400 nm and 3 μm have been successfully obtained. The mechanical properties (hardness and tensile resistance) coupled with corrosion resistance behavior have been then studied as a function of the grain size. The sintered specimens present a strong increase in tensile resistance together with a strong decrease in ductility due to the grain size refinement. The corrosion resistance seems not to be affected by the non-equilibrium sintering process.