Surface defects cause the measured tensile strength of glass and other brittle materials significantly lower than their theoretical values. Here, we describe an on-line process to ‘heal’ surface flaws and functionalise surface properties. A nanometer-scale hybrid coating layer based on styrene-butadiene copolymer with mutiwalled carbon nanotubes (MWCNTs) and/or nanoclays, as mechanical enhancement and environmental barrier layer, is applied to alkali-resistant glass fibres (ARG). The nanostructured and functionalised traditional glass fibres with low fraction of nanotubes or nanoclay (1 wt% in sizing) show significant improvement in both mechanical properties and environmental corrosion resistance. We introduce a healing efficiency factor and conclude that the coating modulus, thickness and roughness are responsible for the mechanical improvement of fibres. Furthermore, we show that the hybrid coating layer is essential for enhanced interfacial adhesion strength of the glass fibre reinforced cement composites.