Fibriform supercapacitors (FSC) are promising energy storage devices for wearable electronics which require excellent durability and fabric-like wearable comfort. In this work, we successfully converted commercial cotton threads (CT) into electrically conductive and electrochemically active threads by introducing reduced graphene oxide (rGO) and carbon nanoparticles (CNPs) using a large-scale producible method (dip-coating combined with low-temperature vapour reduction). The rGO coated CT (rGO-CT) has impressive conductivity which is attributed to the wrapped rGO nanosheets and it is steady enough to tolerate washing process for a long time. After coated with CNPs, the conductivity of CNPs/rGO composites coated CT (CNPs/rGO-CT) has been enhanced tremendously. Meanwhile, the rGO nanosheets with implanted CNPs form the three-dimensional (3D) hierarchical nanostructures which provide abundant ion transmission channels. Furthermore, we have prepared the CNPs/rGO-CT based FSC, which exhibits high volumetric capacitance (3.79 mF cm(-3) at 50 mV s(-1)), well cycling stability (95.23% capacitance retention after 10000 charge-discharge cycles), and excellent electrochemical stability (92.30% capacitance retention after 2000 bending cycles). Especially, the CNPs/rGO-CT based FSC maintains great capacitive performance when it was knitted into textile, thus making it meet the high performance requirements of energy storage devices for knittable and wearable electronics. (c) 2016 Elsevier Ltd. All rights reserved.