An ultrasound-assisted advanced oxidation process (AOP) has been demonstrated for sonocatalytic degradation of methyl orange (MO) with Fe3O4/polyaniline (Fe3O4/PANI) microspheres in near neutral solution (pH similar to 6). The Fe3O4/PANI microspheres were characterized with XRD, SEM, TEM, FT-IR, XPS, and zeta-potential measurements, and were further tested in the role of adsorption and sonocatalytic decolorization of MO in solution. The isotherms and kinetics of MO adsorption with Fe3O4/PANI follow the Langmuir model and the pseudo-second-order model, respectively. The kinetics of sonocatalytic decolorization of MO with Fe3O4/PANI conforms to a combinational model involving the pseudo-second-order adsorption model and the pseudo-first-order degradation model, since Fe3O4/PANI has a high capacity to adsorb MO in solution. The percentage of room-temperature sonocatalytic degradation of MO with Fe3O4/PANI is about 4.8, 8.8, and 5.7 times that with Fe3O4, dedoped Fe3O4/PANI, and ultrasonication alone, respectively. The eco-friendly Fe3O4/PANI featured with superparamagnetism and excellent reusability offers a promising sonocatalyst for rapid decolorization and enhanced degradation of azo dyes in effluents.