The Higgs potential of the minimal nonminimal supersymmetric standard model (MN-MSSM) is investigated within the context of electroweak phase transition. We investigate the allowed parameter space yielding correct electroweak phase transitoin employing a high temperature approximation. We devote to phenomenological consequences for the Higgs sector of the MNMSSM for electron-positron colliders. It is observed that a future e + e − linear collider with √ s = 1000 GeV will be able to test the model with regard to electroweak baryogenesis.1