Researchers recommended geosynthetics material to enhance the performance of paved and unpaved roads, especially those constructed on weak subgrades. There are two types of geosynthetic that most widely used in pavement systems which are geogrids and geotextiles. This study focuses on two primary objectives. First, examining the impact of geogrid (Tensar SS) when reinforcing conventional flexible pavements constructed on subgrade. The second confirms the most optimal location for integrating a pavement system with geogrid. To quantify the effectiveness of a geogrid in flexible pavements structure, 3D finite element simulation was conducted using thick base pavement structure. In order to identify the best location for the installation of geogrid in pavements, two different geogrid locations were implemented. A constant loading condition was applied while the geogrid locations were varied in the proposed pavement structures. This process exposed the effect of geogrid in pavement performance such as the reduction of longitudinal and transverse shear deformation in unbound layers. This study has identified two different conclusions. First, pavement performance can be improved by implementing a single geogrid layer within the upper third of the layer and second, in order to achieve structural stability, the subgrade-base layer interface may require a geosynthetic stabilization layer.