Longitudinal twinning α-In2Se3 nanowires with the (1018) twin plane were synthesized to fabricate high performance single nanowire based photodetectors. As-synthesized α-In2Se3 nanowire exhibited typical n-type semiconducting behavior with an electron mobility of 23.1 cm2 V–1 S–1 and a broadband spectral response from 300 to 1100 nm, covering the ultraviolet-visible-near-infrared (UV-visible-NIR) region. Besides, the fabricated device showed a high responsivity of 8.57 × 105 A W–1, high external quantum efficiency up to 8.8 × 107% and a high detectivity of 1.58 × 1012 Jones under 600 nm light illumination at a basis of 3 V, which are much higher than previously reported In2Se3 nanostructures due to the interface defect effect of the twin plane. The results indicated that the longitudinal twinning α-In2Se3 nanowires have immense potential for further applications in highly performance broadband photodetectors and other optoelectronic devices.1)