The mechanical-elastic-elastic properties, along with the compressive strength, Young’s modulus, and Poisson’s ratio, are the fundamental properties of cementitious material. The experimental measurements require much times for the sample preparation and testing, while predicting these properties is very difficult due to the high complexity of the material. This paper presents a novel approach based on the combination of microstructural modeling and a multi-scale model in order to predict the mechanical-elastic properties of cement paste. The cement hydration is modeled using the CEMHYD3D code, which provides a prediction of the volume fraction of each hydration product. The predicted volume fraction and intrinsic mechanical properties of each component were used as input data in a multi-scale model to estimate the evolution of the mechanical-elastic properties of cement paste. The formation of two types of the calcium silicate hydrate (low-and high-density C-S-H) with different intrinsic mechanical properties was also considered in this study. The CEMHYD3D code could provide the accurate prediction for the cement hydration when compared to the experimental measurement. The modeling result of the multi-scale model indicated that the mechanical-elastic properties of cement paste strongly depend on the evolution of the volume fraction of each component and the spatial gradient distribution of the C-S-H phase. The C-S-H phase plays the most significant role in the development of the mechanical-elastic properties of the cement paste. Using an adequate value of spatial gradient distribution, which could be computed from the calibration of compressive strength, this novel approach could accurately predict the evolution of the elastic properties during cement hydration, including the Young’s modulus and Poisson’s ratio.