Polycarboxylate superplasticiser (PCE) is notably sensitive towards Na-Montmorillonite (Na-Mmt), an impurity generated from the manufacturing of concrete aggregate due to the chemical intercalation and poor surface adsorption. In order to improve the poor compatibility of PCE, the protein-based retarders were applied as the sacrificial agents, and its synergetic effects in cementitious materials containing Na-Mmt were investigated. The protein-based retarders were applied as the sacrificial agents and its synergetic effects in cementitious materials containing Na-Mmt were investigated. In addition to test rheology, minislump, and setting time, the adsorption behaviour and intercalation were characterised via Total Organic Carbon, X-ray photoelectron spectroscopy, and X-ray diffraction. The results revealed that the incorporation of protein-retarders improved the performance of PCE in terms of workability, and the rheological behaviour of cement with Na-Mmt. Moreover, compared to simultaneous addition, the application of separate addition further increased the workability and improved workability retention, with best dispersion performance obtained by prior adding the retarders, which could be due to the lessened intercalation between the layers of Na-Mmt.