Carbon nanotube-reinforced silicon carbide composites (CNT/SiC) produced by direct infiltration of matrix into a porous CNT arrays have been demonstrated to possess a unique microstructure and excellent micromechanical properties. However, the thickness of the array preforms is usually very small, typically less than 2 mm. Therefore, fabrication of macroscopic centimeter-scale CNT/SiC composites by chemical vapor infiltration (CVI) process requires that the nanoscale fillers could form macroscopic architectures with an open pore network. Direct infiltration of matrix into porous CNT sponges consisting of a three-dimensional nanotube scaffold may provide a possible solution to this challenge. Here, the study reports on the fabrication of CNT/SiC composites by CVI of SiC matrix into the open pore network of CNT sponges while maintaining the original CNT network. The unique microstructure, mechanical properties, electrical conductivity, and electromagnetic shielding effectiveness of the resultant composites were systematically investigated. Energy dissipation toughening mechanism at the nanoscale such as CNT pullout is observed, and the phase composition of the fabricated materials includes beta-SiC and CNTs.