The use of p-y curves is heavily engrained into geotechnical engineering practice. However, even with the prevalent use of p-y curves, these are only used to model the loading portion and not the unloading of a load test or loading demand in the field. A review of the literature shows that available software commonly used to model the problem of laterally loaded piles is used for loading and not unloading. Thus, there is a knowledge gap in the research for the unloading phase for laterally loaded piles. This thesis presents a method that has been developed to model the unloading behavior of a laterally loaded and unloaded single pile. A program has been developed using MATLAB that uses a 1D finite element model (FEM) for the pile and non-linear p-y curves to model the soil reaction in this soil-structure-interaction problem. The proposed method is based on a secant stiffness degradation model that models the soil and structure as a single system with a degrading stiffness. The method has been numerically implemented and validated with experimental data of a lateral load test involving loading and unloading.