In this work, the ferrimagnetic nickel-zinc ferrite nanopowder was synthesized via citrate-ethylene glycol processing, followed by the preparation of the epoxy-based nanocomposite. The materials were characterized using X-ray diffraction (XRD), simultaneous thermal analysis (STA), alternative gradient force magnetometer (AGFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the sample calcined at 1000 degrees C for 1 h had the best crystallinity, and the calculated crystallite size of this sample was similar to 105 nm. The rheological properties and the magnetoviscous effect of the nanocomposites were studied by a standard rotating rheometer. The effects of the magnetic fields and shear rate with respect to time were investigated, and the results were discussed in terms of aggregates and magnetic field-induced structures. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 2534-2539, 2012