Abstract: Carbon nanotubes (CNT) were assembled onto the surface of the micro-fibers of nylon veil (PAV) with good viscoelasticity using a spraying process, resulting in CNT-decorated nylon veil (PAV@CNT). Subsequently, carbon fiber/vinyl ester resin (CF/VE) composites interleaved with PAV or PAV@CNT were fabricated using the vacuum-assisted resin infusion process. The microscopic morphology of the PAV and PAV@CNT, as well as the interlaminar fracture morphology of the CF/VE composites, was characterized. The effects of the interleaving modification on interlaminar fracture toughness, mechanical properties, and damping performance of the CF/VE composites were systematically investigated. The results indicated that, compared to the non-interleaved reference sample, the CF/VE composite interleaved with PAV having an areal density of 16 g/m² (PA16V) exhibited increases in Mode I (G_IC) and Mode II (G_IIC) interlaminar fracture toughness, and average loss factor (tanδ_ave) by 38.9%, 86.4%, and 31.3%, respectively, demonstrating a simultaneous enhancement in interlaminar toughness and damping performance. After CNT modification, the CF/VE composite interleaved with PA16V@CNT showed significant improvements in G_IIC and tanδ_ave, which were increased by 119.7% and 50.6%, respectively, compared to the non-interleaved reference sample. This significant enhancement results from the synergistic reinforcement between the nano-CNTs and micro-PA fibers, where energy is dissipated via multiphase interfacial interactions among CNTs, resin, and PA fibers, along with the energy dissipation mechanism arising from CNT interfacial friction and sliding deformation. Additionally, the PA16V@CNT interlayer had a slight effect on the flexural and compressive strengths of the CF/VE composites.