Ultrafine nanotubes of Cu2NiSnS4 having an average diameter of 4 nm were prepared by a convenient one‐step nanoconfined solvothermal approach. The confined reaction took place within the pores of anodic aluminum oxide (AAO). The structure, morphology, composition, optical absorption, and magnetic properties of the as‐prepared samples were characterized using X‐ray powder diffraction, transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, scanning electron microscopy, UV/Vis spectroscopy, and superconducting quantum interference device measurements. A Rolling‐up mechanism was proposed to explain the formation of Cu2NiSnS4 nanotubes. Thin films prepared from the nanotubes showed a photoelectric response, thus indicating a potential application for photovoltaic devices.