Recently, graphene and carbon nanotubes (CNT) hybrids stimulated the development of advanced composites. Especially, the electrochemical activities of CNTs or corresponding hybrids have been greatly improved via functionalization. In this work, we developed a self-assembled graphene and carbon nano-tube hybrids with interconnected network of carbon structures, which was applied to fabricate a modified carbon paste electrode (CPE) for electrochemical sensor with well-response and specificity. In square wave stripping voltammetry (SWSV), the relative current of the proposed sensor was linearly proportional to the concentration of Cu2+ in the range of 0.02 to 11.10 mu M and 31.10 to 111.1 mu M with a detection limit (DL = 3S/k) of 0.0095 mu M, which was better than the reported for other carbon-based materials. These advantages might be attributed to the cooperation of the large surface area for the adsorption and the electron transfer of hybrids for Cu2+. The proposed electrochemical sensor exhibited excellent analytical performance with high sensitivity and selectivity. Finally, it was applied to detect Cu2+ in the tap water and pond water with high accuracy and good recovery. Results indicate the hybrids prepared here may provide an effective strategy for electrochemical sensors. (C) 2016 Elsevier B.V. All rights reserved.