This paper presents the results of three-dimensional (3-D) finite element analysis of a monitored geogrids-reinforced embankment constructed on soft clay formation and supported by cast in-situ piles. The analyses were conducted using the software PLAXIS 3D. A comparison between the predicted and monitored responses is presented to assess the adequacy of the adopted numerical model. The model was used in a parametric study to investigate the effect of key aspects of the embankment on the efficiency of the piled embankment. Moreover, a comparison was performed between the results of the 3-D analyses and the analytical solutions. This paper concluded that the effect of using pile caps decreased both the total and differential settlement and increased the efficiency of the piled embankment system. The study of using geogrids revealed that it can contribute to decreasing the settlement and maximizing the part of the embankment load transferred to piles. Moreover it was found that increasing the stiffness of the geogrids provided higher values of tensile forces, and hence has more influence on the embankment loads carried by piles rather than using multiple layers with lower stiffness. The efficiency of the piled embankments system was also found to be greater when higher embankments are used rather than the low height embankments. The comparison between the numerical (3-D) model and the theoretical design methods revealed that many analytical solutions are nonaccurate compared to the (3-D) finite element numerical.