A three-degrees of freedom (3-DOF) coupled numerical simulation technique for synchronously extracting 18 aerodynamic derivatives of bridge decks is proposed and evaluated in this study. Computations are performed with a finite volume unstructured computational flow dynamics (CFD) solver using two-dimensional (2D) hybrid meshes with fine near-wall resolution. The accuracy of the numerical model is verified by identifying the aerodynamic derivatives of one thin plate section with theoretical solutions. Further, for two typical deck sections (streamlined and bluff) of two long-span bridges, the extracted 18 aerodynamic derivatives from both coupled and uncoupled techniques are compared. The results showed good agreement with the experimental results. The proposed 3-DOF coupled method can provide almost the same level of accuracy as the 1-DOF method and saves about 67% of the computation time. The appropriateness of the linear superposition theorem for the aeroelastic forces generated by different motions (single and coupled mode) is examined, and found that there are significant differences in both aerostatic and aeroelastic forces. Various high-order aeroelastic force components are successfully captured by the newly presented coupled numerical simulation, and the aerodynamic derivatives are proved to be immune to the high-order components mathematically. This knowledge is essential for a thorough evaluation of aerodynamic derivatives identification accuracy. The proposed technique and the analytical viewpoints presented in this paper may serve as the building block for developing new numerical tools and analytical frameworks for rapid and accurate evaluation of aerodynamic derivatives, and the response of long-span flexible bridges to wind excitation. (C) 2014 American Society of Civil Engineers.