The use of biomaterials as implantable thermoseeds under the action of an external magnetic field is a very interesting methodology to focus the heat into the target tumors as osteosarcoma. In this study, biocompatible and bioactive G15GC85 thermoseeds, tailored through the combination of sol–gel glasses (G) with a magnetic glass ceramic (GC), were used to induce hyperthermia on cultured human osteosarcoma cells after exposition to alternating magnetic field (MF, 100 kHz/200 Oe). G15GC85 magnetic glass–glass ceramic thermoseeds induced in vitro effective hyperthermia with drastic reduction in proliferation of human osteosarcoma Saos-2 cells and high increase of apoptotic cells after two 40 min consecutive sessions of MF. Deep cell morphology alterations were observed after this hyperthermic treatment, and the proteomic analysis revealed modification of gamma actin molecular properties related to cytoskeleton alterations. These results indicate that G15GC85 thermoseeds allow to induce in vitro effective hyperthermia on human osteosarcoma cells. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A:, 2012.