Superparamagnetic iron oxide nanoparticles (SPIONs) are known to be good MRI contrasts, but they have a high tendency to aggregate and their biocompatibility is limited. Hyaluronic acid is highly biocompatible, can provide SPION with colloidal stability, and interacts specifically with tumor cells through the CD44 receptor; therefore, it was used as a stabilizing layer. We successfully obtained SPION coated with hyaluronic acid and further functionalized it with folic acid to construct a dual-targeted system. The physicochemical properties of the nanoparticles were investigated using DLS/ELS, AFM, XRD, and ATR-FTIR. Their magnetic characterization was performed by magnetometry, Mössbauer spectroscopy, H NMR T1 and T2 measurements, and MRI. The nanoparticles’ biocompatibility was verified on blood and hepatocytes, and their cytotoxicity was tested on glioma and adenocarcinoma cells using the MTT assay. The nanoparticles were spherical, colloidally stable, and had low dispersity. Their cores were formed by 7 nm crystallites of magnetite in its oxidized form, maghemite. Our SPIONs were superparamagnetic and could potentially serve as effective T2 contrasts for MRI. The performance of SPIONs modified with folic acid was superior to that observed for commercial contrasts. Our nanoparticles were also hemocompatible and were efficiently taken up by glioblastoma cancer cells. Folic acid-modified SPIONs could also reduce viability of tumor cells in a dose-dependent manner. Thus, the proposed system has potential application as both a diagnostic tool and a therapeutic agent for targeted anticancer therapies.