This study aims at implementing an interfacial model to capture the role of interfaces in polyester-based composites reinforced by metallic fibres. A pull-out test of single aluminium and steel fibres embedded in unsaturated polyester matrix is performed. Finite element computation is performed to simulate the typical response of the pull-out test based on an interfacial model. The implemented model relies on a nonlinear relationship assumed between the interfacial shear and interfacial separation. A sensitivity analysis is conducted to reveal the effect of each parameter of the interfacial model. The identification of these parameters with respect to the experimental conditions is also attempted. The predictions show a perfect matching with the experimental trends if a two-term expression is accounted for as an interfacial response. The model outcome reveals superior interfacial performance of the aluminium/unsaturated polyester composite.