The study on the migration behaviour of light non-aqueous phase liquid (LNAPL) through the subsurface system is essential for implementing a proper remedial measure against groundwater contamination. A FEM-based flow and transport model FEFLOW (Finite Element subsurface FLOW and transport system) was utilised in this study to model the migration of LNAPL, through the unsaturated zone, where the LNAPL is modelled as a single-phase contaminant with the least water solubility. Further, it evaluates the utility of a natural fibre, coir geotextile (CG) in controlling the migration of the LNAPL through the subsurface system based on an experimental study. The predictions from the numerical model are compared and found matching with the experimental results. The CG layer is also modelled similarly to the soil layer with appropriate values of the parameters, which defines the novelty of this study. Hence, the developed numerical model is used to simulate the actual field conditions to assess how long the coir geotextile can sustain as a remedial measure for controlling LNAPL migration through the soil. The provision of two layers of CG with a vertical layer on both sides as a box-like containment could hold LNAPL up to 7.5 years in the wet condition and 5 years in the dry condition of soil.