The growing desire for better polymer-based composites has given rise to increasing research in the production and modeling of natural fiber-reinforced polymer composites. In this work, the effective elastic properties of unidirectional banana fiber-reinforced polystyrene composites were evaluated via a numerical homogenization approach. Properties such as longitudinal modulus, transverse modulus, in-plane Poisson ratio and in-plane shear modulus were affected by parameter such as fiber volume fraction and cross section. The predicted numerical results obtained via finite element analysis were in good agreement with the existing phenomenological analytical model predictions.