Basalt fibers were functionalized by ZnO electroless deposition for obtaining a nanostructured interphase for enhancing the interfacial strength with an epoxy resin matrix. The structural, morphological and wetting properties of the pristine basalt fabrics and ZnO-coated basalt fabrics were evaluated. The fabrics were uniformly coated with ZnO nanostructures featuring a wurtzite structure and a twin hexagonal prism morphology. The contact angle measurements revealed that ZnO prisms transformed the hydrophilic basalt fabric into a hydrophobic one (~130°). ZnOs were also grown on the basalt fibers as yarns to evaluate their interfacial adhesion by single fiber pull-out tests. The results emphasize significant improvement in the apparent interfacial shear strength (~42%) with limited degradation of the pristine basalt fiber tensile strength (a reduction of ~ 17%). Therefore, ZnO electroless deposition can be regarded as an effective route to improve the mechanical performance of basalt/epoxy composites expanding their potential range of applications as structural materials.