In this paper we present a study on the coupled effect of the aging and the surface treatment on the fracture and tensile properties of a glass/vinyl ester layer. The chemical treatment of the glass fiber's surface determines directly the interface properties and indirectly the mechanical behavior of the composite. It plays an important role in the resistance of the composite against the attack of water molecules. Results obtained by tensile and mode II fracture tests show the evolution of the tensile and fracture properties with the water content rate and the surface treatment. Observations made by optical and scanning electron microscope give complementary interesting information about the damage and the crack propagation mechanism. Our aim was to understand the evolution of the mechanical properties of the composite in function of the interface. Tensile and mode 11 interlaminar fracture tests were performed on specimens having three kind of surface treatments and four different levels of water content rate. Graphs showing the evolution of the mechanical properties and photos taken by electronic microscope on the shear crack surface and the fiber-matrix interface crack are presented.