In this study, we demonstrate the effects of surfactants on the morphology of Nb2C MXene-derived ferroelectric KNbO3 crystals. We synthesized plate-like KNbO3 crystals using Nb2C MXene and KOH as niobium and potassium sources, respectively, and sodium dodecyl sulfate as the surfactant. In addition, we conducted the same hydrothermal process for Nb2C MXene and KOH as niobium and potassium sources, respectively, and benzyltriethylammonium chloride as a surfactant; we found that the final product exhibits bulk morphology. We show that the morphology of MXene-derived KNbO3 crystals is strongly related to the interaction between the MXene flakes and the functional groups of the surfactant during the hydrothermal process.