A novel template-free hydrothermal approach has been developed to synthesize metastable alpha-phase copper phthalocyanine (CuPc) nanobelts, which can be realized under a mild condition with a low reaction temperature. The morphology of CuPc nanobelts at different growth stages was observed using field emission scanning electron microscopy. The structures were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and X-ray diffraction. Results show that as-synthesized alpha-CuPc nanobelts possess well-crystalline structure with diameters of about 100 nm and long lengths above 50 mu m. In addition, a self-assembly formation mechanism of CuPc nanobelts has been briefly discussed.