This work investigates the humidity influence on the polyester/glass fiber composite material containing fillers (ASP 400). The materials are exposed to both distilled and sea water at 45 degrees C. The moisture diffusivity and the moisture equilibrium reached by this composite were determined by using the gravimetric test method. Experiments results indicate that the distilled water diffuses in all composite much more rapidly than the sea water [H. Ben Daly, H. Ben Brahim, N. Hfaiedh, M. Harchay, R. Boukhili, Polymer Composite, 28,355-364, 2007]. In order to probe the effect of moisture absorption at the interface, mechanical measurements are performed using the nano-indentation test. (C) 2008 Elsevier B.V. All rights reserved.