A highly sensitive ascorbic acid (AA) sensor based on hierarchical nanotube structured polyaniline (PANI)-halloysite nanotubes (HNTs) composites is reported. The PANI/HNTs electrode is electrophoretically deposited from the colloidal suspension of PANI/HNTs nanotubes which are obtained via chemical oxidative polymerization of aniline on HNTs. The electrode is a uniform and compact film with a porous structure, which is created with the 3-dimensional network-like coaxial nanotubes. It is the first report of such structure to the best of our knowledge. This PANI/HNTs sensor exhibits unprecedented sensitivity towards AA as high as 826.53 mu A mM (1)cm (2) within a linear range of 0.005 to 5.5 mM, and a low detection limit of 0.21 mu M. This ideal sensing performance could be ascribed to the porous structure affording efficient sensing channels for improving electron transport and interactions between the PANI and AA. These results demonstrate that PANI/HNTs hierarchical nanotubes are promising materials for electrochemical sensor applications. (C) 2017 Elsevier Ltd. All rights reserved.