Superparamagnetic iron oxide (Fe₃O₄) nanoparticles have been investigated for decades due to their potential biomedical applications. In this study, we synthesized, characterized and biologically tested multifunctional Fe₃O₄-based drug delivery systems for such an application. The nanosystems were successfully prepared with a small size, high saturation magnetization and high drug loading. The Fe₃O₄ core in an alternating magnetic field could generate enough heat for both effective hyperthermia therapy and doxorubicin release from the alginate shell for chemotherapy. Also, a folate factor was attached to the nanoparticles to help the system to enter and stay in the tumor cells for a longer time. In vivo experiments showed that the combined treatment was very helpful for the survival of lung cancer-bearing mice, especially in the case of the presence of a folate factor.