The experiment and nonlinear FE analysis of concrete beams prestressed with external tendons were performed to investigate the flexural strength, the tendon stress, and to propose the equation for evaluating the tendon stress. Several parameters were examined in order to evaluate the significance of influential parameters. The analytical results were validated with the experimental investigations carried out in this study. From the parametric study, it indicates that the span-to-depth ratio has less significant effect on the tendon stress. However, the geometry of applied load must be taken into account for evaluating the tendon stress. Finally, the design equations to predict the tendon stress of such beams were proposed.