Magnetic properties of fine Sr2 FeMoO6 (SFMO) powders were systematically studied and superparamagnetism was observed. The SFMO samples were prepared using a citrate-gel method and were characterized by X-ray diffraction (XRD), ferromagnetic resonance (FMR) and Mössbauer spectroscopy. The XRD measurements showed that the powders are nearly pure and the Rietveld refinement gave particle sizes of 31 and 197 nm and antisite disorders of 10 and 15%, respectively. The 197 nm crystallite size sample has a TC = 415 K and a magnetic moment of 3.0 μB / f . u. Several measurements made by SQUID magnetometer, FMR and Mössbauer spectroscopy showed that the 31 nm crystallite sample behaves superparamagnetically with blocking temperature TB = 35 K and it has a reduced saturation magnetization of 1.0 μB / f . u . at 5 K and effective paramagnetic moment of 3.0 μB.