In this study, we switched from using dexamethasone sodium phosphate (DEX) injection (brand-name product), which is administered to reduce nausea/vomiting related to cancer chemotherapy, to a generic drug, considering its pharmaceutical features: the generic drug does not contain paraben as an additive, and it may be stored at room temperature, whereas the brand-name formulation must be stored in a cool place. We compared the clinical effects of the brand-name and generic formulations of DEX injection on nausea/vomiting related to therapy with cisplatin, which frequently causes nausea/vomiting, based on the nausea/vomiting inhibition rate. There was no significant difference in the inhibitory effects on acute or delayed nausea/vomiting. Furthermore, there was no significant difference in the frequency of treatment with first-aid agents, which were administered when the inhibitory effects were insufficient. These results suggest that the clinical effects are similar between brand-name and generic formulations of DEX injection. Generic formulations may be useful with respect to their cost and application.