Fe3O4/ZnO heterostructures that composed of Fe3O4 cubes and ZnO nanowires were successfully synthesised through a facile two-step hydrothermal method. The obtained heterostructures were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). SEM results showed that ZnO nanowires with length of about 2 μm were successfully grown onto the magnetic Fe3O4 cubes. Vibrating sample magnetometer results showed that the saturation magnetisation (Ms) value of the heterostructures is 87.7 emu g− 1. Room temperature photoluminescence (PL) spectra of the obtained heterostructures were also investigated and the results showed a strong UV emission centred at about 380 nm, which can be attributed to the ZnO nanowires. The as-prepared Fe3O4/ZnO heterostructures exhibit both excellent magnetic and perfect optical properties, which will endow their great potential applications in the spintronics and magnetic-fluorescent fields in the future.