A method is presented for modeling the tensile behavior of multifilament twisted yarns. A filament assembly model and a computer-aided design/computer-aided engineering (CAD/CAE) approach are proposed for the tensile analysis. The geometry of the twisted yarn and the nonlinear filament properties were considered. The finite element method (FEM) and large deformation effects were applied for computation of the stress-extension curves. Ideal yarn structures of five layers with different twist angles were simulated to predict the tensile behavior of each filament and each layer. The stress acting on the filaments after yarn extension could be directly analyzed by the FEM. The stress distribution in the filaments showed that the highest stress regions were located at the filament in the center of the yarn and decreased slightly to the yarn surface. The stress-extensions of the filaments were converted to yarn tensile behavior that is shown in terms of the maximum and average stress-extension curves. The results of this prediction model were compared with the stress-strain curves of high-tenacity rayon yarn and the energy method. The maximum stress-extension curves showed very good agreement with experimental results and are more accurate than those obtained by previous methods.