Casein (Cas) has recently attracted attention as a vehicle for curcumin (Cur), but organic solvents are generally used to prepare the complex. In the present study, preparation of the complex between Cur and Cas (Cur-Cas) under neutral conditions by kneading without using organic solvents was studied from the viewpoint of safety and cost. The water dispersibility of Cur-Cas increased as the mixture was kneaded at higher temperature. The apparent water solubility of Cur-Cas was equal to or greater than those of Cur complexes prepared using other dispersants. From the results of zeta potential, Cas dominates the surface charge of Cur-Cas, and Cur-Cas shows higher dispersibility at pH more than 5.7, at which it is negatively charged. Cur-Cas was present as a hydrocolloidal material and the particle size was around 300 nm. Characterization of Cur-Cas by differential thermal analysis and X-ray diffraction showed that the crystallinity of Cur was decreased by the complexation with Cas.