In nature, the mechanical properties of soils, vary from region to region and in some areas, high-strength soil resources lack is a serious difficulty that geotechnical engineers may face where constructing earthworks such as railway and road embankments is required. Although a wide range of soil improvement techniques exists to improve such soils, the effect of geocell, as an effective solution, has not yet been investigated for railway embankments, hence, the present study aims to develop a three-dimensional (3D) Finite Element (FE) model, to fill the gap. To do this, first, six, 1/20 scaled-down railway embankments, including an unreinforced and 5 reinforced ones, were constructed in the lab and their load-settlement behavior, was assessed. Second, a 3D FE model was validated by experimental results and then, using a parametric study, the effect of geocell opening size and geocell layers number, were investigated on bearing capacity and settlement of the embankments, for five various types of soil ranging from poor soils (ST1), to high strength soils (ST5). The outcomes indicated, although adding geocell layers up to 15 layers, results in reducing the exerted stress in railway embankments by a maximum of near 50%, the crest settlement is not efficiently affected. Moreover, it was found that geocell’s opening size has a negligible effect on decreasing the embankment’s settlement, while it affects the bearing capacity significantly, up to a maximum of 50%.