We report a template technique for the fabrication of high density nanocrystalline diamond (NCD)-coated silica (a-SiO2) nanofibers with diameters of 1–5 μm. This method includes the synthesis of templates (a-SiO2 nanofibers) by conventional Vapor–Liquid–Solid method and the conformal coating of the nanofibers with nanodiamond by Microwave Plasma Chemical Vapor Deposition technique in hydrogen-deficient conditions. A detailed micro-structural analysis was performed to probe the interaction of the NCD grains with a-SiO2 nanofibers. The specimen for Transmission Electron Microscopy was prepared using Focused Ion Beam lift-out method. Room temperature micro-Raman was performed to study the crystalline quality of the NCD-coated silica nanofibers. Field electron emission of as-synthesized NCD-coated silica nanofibers was observed with a threshold field of ~ 3 V/µm.