The synthesis of magnetic protein nanospheres via a modified sonochemical route was described. The effects of experimental parameters, such as bovine serum albumin dosage, ferrofluid concentration, ferrofluid dosage, ultrasonic power and time on the morphology, and dispersibility of magnetic protein nanospheres, were investigated. The final magnetic protein nanospheres were characterized by Fourier-transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, and vibrating sample magnetometer. The results showed that the superparamagnetic protein nanopsheres had small particle size of 100 nm, high saturation magnetization, high magnetite content, and abundant functional groups. These biocompatible protein nanospheres have biomedical applications. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012