The paper presents water absorption and its effect on the tensile properties of hybrid of fly ash-CaCO3-filled epoxy. The total filler content was 20wt%, with the fly ash to CaCO3 ratios were 20/0, 15/5, 10/10, 5/15 and 0/20. Adding fillers into epoxy decreased the water uptake in the ranges of 15 - 22%, where the lowest and the highest water uptake of the hybrid systems belonged to the fly ash/CaCO3 ratios of 15/5 and 20/0, respectively. The tensile strength and elastic modulus continued to decrease with aging time for all epoxy systems. At the saturation level, the tensile strength and elastic modulus of filled epoxies were improved compared to the unfilled epoxy, except for the hybrid of fly ash/CaCO3 of 15/5. The fracture strain as well as the tensile toughness were considerably increased at the equilibrium. A scanning electron microscopy revealed that in dry condition the fly ash was well bonded with the matrix, but not for the CaCO3 particles. In the semi equilibrium and equilibrium states, the fly ash and CaCO3 were mostly detached from the epoxy. The hybrid of fly ash/CaCO3 of 15/5 was not recommended as it decreased the tensile properties more than the other hybrid compositions.