Fabrics that allow selected microwave frequencies to pass through, called frequency selective fabric composites (FSFCs), were fabricated by weaving carbon fibers and dielectric fibers in periodic patterns. Design parameters affecting the electromagnetic characteristics (EM) of the FSFCs were widely discussed with respect to electrical conductivity of carbon fibers, the type of dielectric fiber and matrix, and weaving patterns. Transmission coefficients of square FSFCs with the aperture sizes of 10 mm and 20 mm were investigated considering electrical conductivity of carbon rovings, fiber undulation, and aperture-to-cell ratio. Compared with metallic frequency selective surfaces (FSSs), lower electrical conductivity of the carbon rovings caused a partial transmission near resonance frequency. The fiber undulation made little effect on the electromagnetic property of FSFCs. In addition, as the aperture-to-cell ratio decreased, the transmission of microwaves through FSFCs substantially decreased around resonance frequencies. The distinct difference in the microwave property of FSFC and FSS near resonance frequency shows that FSFCs can be new candidates as impedance modifier for microwave devices, such as microwave absorbers.