In recent years, nano/ultrafine grained steels have been the focus of great attention for the construction of lightweight structures. In this work, the effects of thermo-mechanical parameters were investigated in order to achieve a nanocrystalline structure in the as-cast AISI 301 stainless steel. A minimum grain size of 18 μm was initially achieved when homogenization took place at 1200 °C for 9 h followed by hot rolling at a temperature range of 1000–1200 °C with a strain value of 0.8 and a strain rate of 1.2 s−1. The product was then annealed at 1050 °C for 3 min. In order to get a nanocrystalline structure, repetitive cold rolling followed by subsequent annealing was used. The cold rolling was carried out at a temperature of −10 °C with a strain rate of 0.5 s−1 and a reduction of 95%, while the annealing treatment was conducted at temperatures of 600 to 850 °C for 0.5 to 50 min. The results showed that the nanocrystalline austenitic structure with a grain size of about 70 nm was obtained by annealing at 850 °C for 1 min after an overall cold rolling reduction of 95%.