WO3.H2O nanotubes are successfully synthesized with the aid of intercalated polyaniline (PANI) under relatively mild conditions. More interestingly, the WO3.H2O nanotubes have a rectangular cross-section structure formed through a rolling mechanism. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared analysis, UV-vis-near-IR spectroscopy, selected-area electron diffraction, and vibrating-sample magnetometry analysis are employed to characterize the morphology, structure, and properties of the nanotubes.