The majority of fission products in SNF can be separated during the oxidative dissolution in Na2CO3–H2O2 solutions through alkaline spent fuel reprocessing. However, since some fission products like Cs, Tc, Mo, and Te can be completely dissolved in a carbonate solution, they can not be removed during the extraction step of alkaline spent fuel reprocessing. In this work, a pretreatment step using sodium hydroxide solution has been investigated in order to remove these dissolved fission products in advance. At 25 °C, after 60 min, the results showed that the dissolution rates of Мо, Cs, Ba, Re, and Te were enhanced with the increase of NaOH concentration. However, the dissolution rate of UO2 and U3O8, respectively, decreased from 0.191% to 0.026% and from 0.223% to 0.035% at 85 °C, after 60 min. The dissolution rate of UO2 and U3O8 was decreased to 0.004% and 0.007%, respectively. Thus, the obtained results demonstrated that NaOH pretreatment for the SNF is considered an effective pre-step in selectively dissolving these fission products before moving to the oxidative dissolution step, as well as improving the reprocessing efficiency in order to minimize dissolution challenges during the different extraction stages.