Epoxy/basalt fiber composites were modified by 2D montmorillonite (MMT), 0D nanoSiO(2), or 2D MMT/ 0D nanoSiO(2) double nanoparticles. Mechanical tests showed that all the modified composites had considerably improved interlaminar shear strength and notch impact strength compared with the unmodified epoxy/basalt fiber composites, and that the double nanoparticle-modified composites displayed the greatest improvement. X-ray diffraction, transmission electron microscopy, and scanning electron microscopy revealed that co-addition of 2D MMT and 0D nanoSiO(2) into epoxy/basalt fiber composites produced a unique microstructure. The MMT was completely exfoliated into nanoscale mono-sheets and interacted with nanoSiO(2) particles to assemble into networks. The networks trapped many epoxy molecules within them and they tightly surrounded basalt fibers to form buffer layers. These results indicate that double nanoparticles of different dimensionality promote epoxy molecules to infiltrate between, combine with and coat basalt fibers more effectively than single nanoparticles, which facilitates better cooperation of epoxy and basalt fibers in resisting external forces. Modification with dimensionally different nanoparticles is an effective pathway to improve the performance of epoxy/basalt fiber composites and broaden their application fields. POLYM. ENG. SCI., 59:730-735, 2019. (c) 2018 Society of Plastics Engineers