In this study, water sorption of resins and composites containing Bis-GMA and TEGDMA in various proportions were measured, and the influence of degree of conversion and the hydrophobicity of the material on the water sorption characteristics of Bis-GMA/TEGDMA resins were evaluated. Unfilled resins and composites containing Bis-GMA/TEGDMA, with a ratio of 1/1, 2/1, or 3/1 by weight, were prepared and cured. Water uptake and the degree of conversion of each specimen were determined, and the hydrophobicity was compared by measuring the contact angle of water. Both unfilled resins and composites containing Bis-GMA/TEGDMA in the ratio of 1/1 showed significantly greater water uptake than the others. The degree of conversion of the specimens increased as the proportion of TEGDMA was increased, and no inverse relationship was found between the water sorption and the degree of conversion. In contrast, the contact angle of the 1/1-specimen was less than the others, demonstrating significant correlation with the water uptake. These findings indicate that Bis-GMA/TEGDMA resins showed the greatest water uptake at the ratio of 1/1, and the water sorption characteristic was not influenced by the degree of conversion but mainly by the hydrophobicity of the material.