Here, the continuous production of carbon nanotube-grafted-quartz-fibres was performed in an open chemical vapour deposition reactor with continuous in line catalyst deposition. Highly graphitic carbon nanotubes (CNTs) with controllable lengths ranging from 0.1 μm to 20 μm were grown on the quartz fibre surface by adjusting the reduction and growth times, with shorter fibres growing homogeneously and longer CNTs growing in a splayed “Mohawk” manner. The effect of CNTs length (and thus microstructure) upon the mechanical properties of CNT-grafted-quartz-fibre/epoxy composites was investigated through single fibre pull-out test. The presence of a uniform coverage of sub-micron long CNTs led to an increase in interfacial shear strength of 11% and 29% when compared to sized and de-sized quartz fibres, respectively.