Rectangular AgIn(WO4)2 nanotubes with a diameter range of 80 to 120 nm and length up to 2 µm have been synthesized by a hydrothermal method. These nanotubes exhibit interesting white light emissions when using 320 nm as the excitation wavelength. A photocatalytic reaction for water decomposition to evolve H2 was performed under UV irradiation, and the rate of H2 evolution is nearly seven times that of the sample prepared by a solid-state reaction, which shows much higher photocatalytic activities compared with their bulk counterparts. The activity of AgIn(WO4)2 nanotubes for degrading rhodamine B in water irradiated by UV light was about twice that of using bulk materials. The formation mechanism of the rectangular nanotubes is proposed based on the anisotropic intrinsic crystalline structure of AgIn(WO4)2. The enhancement of the photoelectric properties is attributed to the nanometer-scale size and tubular structure.