Conventional cancer therapy methods are thought to be replaced by photothermal therapy in near future due to less invasive, less consuming, and highly selective therapeutic features of the latter. Implementing photothermal therapy in practice requires development of multifunctional and efficient photosensitizing agents. The purpose of this study is to develop a magnetic nanocomposite with excellent photothermal performance. A ternary nanocomposite (S-rGO-Fe3O4-PANI) was synthesized by a facile two-step method, including solvothermal co-reduction of graphene oxide and iron nitrate followed by in situ polymerization of PVA stabilized polyaniline. The nanocomposite was characterized with UV-vis, FTIR, XRD, VSM, and SEM, and photothermal properties were investigated with an 808 nm NIR laser. 1 mL of the aqueous dispersions of the nanocomposites at 25, 50, and 100 mu g mL(-1) concentrations were irradiated at 1.5, 2.0, and 3.0 W.cm(-2) laser power densities. Photothermal conversion efficiency was calculated by time constant method and 86.3 % efficiency was obtained from the 100 mu g mL(-1) nanocomposite at 2.0 W.cm(-2) laser power density with a maximum temperature difference of 56.7 degrees C. S-rGO-Fe3O4-PANI demonstrated excellent photothermal performance and is a promising candidate for photothermal therapy, targeted delivery, and imaging applications.