Chalcopyrite CuInSe₂ nanowire arrays have been prepared via a convenient one-step solution approach using porous anodic aluminium oxide (AAO) as a hard template. The as-prepared highly oriented CuInSe₂ nanowires are uniform and single crystalline with a [112] growth direction. The diameter of the CuInSe₂ nanowires is tunable and determined by the pore size in the AAO template. The structure, morphology, composition and optical absorption properties of the as-prepared CuInSe₂ samples were characterized using X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning electron microscopy and UV–Vis spectroscopy. A possible formation mechanism of the CuInS₂ arrays is proposed. Homogeneous nucleation is believed to occur within AAO pores during the reaction and lead to the formation of single crystalline CuInSe₂ nanowires.