We have synthesized the magnetic NiFe2O4 nanosheets using a solution method in the presence of hexamethylenetetramine (HMTA). Morphologies, composition and structure of the as-synthesized samples are characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD), respectively. Fourier transform infrared (FTIR) spectroscopy and vibrating sample magnetometer (VSM) are used to investigate the surface properties and magnetic properties of the NiFe2O4 nanosheets. FE-SEM results show that the NiFe2O4 nanosheet samples have irregular shape with thickness of about 30 nm. XRD result confirms that the samples belong to the cubic crystal system with an inverse-spinel structure. The NiFe2O4 nanosheets possess sub-ferromagnetism with a negligible coercivity and remanence at room temperature. It could become novel magnetic materials with the potential application in sensors, catalyst, and microwave devices.