Polymer nanofibers are increasingly being used in broad and diverse areas. In addition to the intrinsic chemical properties of the polymer, the physical and mechanical properties of the fiber are also important in determining its suitability for a given application. But measuring the mechanical properties and understanding their relationship to the structure and dimensions of the polymer nanofibers present some unique challenges. The atomic force microscope (AFM) has the force-sensing sensitivity and three-dimensional (3-D) spatial resolution necessary for this type of experiment. Several methods have been developed based on the AFM. The threepoint bending test approach is one of the most common, and several models have been developed for results interpretation.