In the current study, the effect of the thickness and the foam density in three-dimensional integrated woven sandwich composites on quasi-static mechanical properties under three-point bending was investigated. Bending modulus and core shear modulus were determined by subjecting the samples, which were cut with varying span lengths according to their core thicknesses, to three-point bending test. Obtained results were optimized by taking core thickness, foam density and panel weights into consideration. Damages that occurred on the tested samples were reported. When compared to conventional foam core sandwich composites, it was found that three-dimensional integrated sandwich composites have superior mechanical properties and due to the fact that the pile yarns in the core and the foam support each other, contrary to conventional sandwich composites no catastrophic core breakage occurs under load, thus the load bearing capacity of the structure is sustained.