Nickel-based single crystal superalloys (SX) are key materials for the manufacturing of blades and vanes of industrial gaz turbines and aircraft engines. These materials are commonly casted using directional solidification Bridgman method to achieve a single crystal structure. This study aimed to determine the impact of bimodal microstructure on tensile and creep properties of nickel based SX superalloys. Following conventional heat treatments for CMSX-4 superalloy, additional heat treatments were applied to generate bimodal microstructures. Tensile and creep tests were performed from room temperature up to 1050°C. Creeps tests performed at 850°C / 575 MPa indicate a significant reduction of creep lifetime for the specimen with a bimodal microstructure with an important primary creep stage and deformation compared to the reference specimen with regular microstructure. Creep and tensile performances as well as the study of tertiary precipitates stability will be discussed in the final paper.