In the present study, a facile one-pot hydrothermal method is introduced for preparation of hyaluronic acid-coated FeO nanoparticles (FeO@HA NPs) for theranostic applications. In the proposed method, hyaluronic acid acts simultaneously as a biocompatible coating layer and as a targeting ligand for CD44 receptor overexpressed on the surface of breast cancer cells. The obtained product with narrow hydrodynamic size distribution exhibited a high colloidal stability at physiological pH for more than three months. Cytotoxicity measurements indicated a negligible toxicity of the prepared sample against L929 normal cells. Preferential targeting of FeO@HA NPs to CD44-overexpressing cancer cells was studied by comparing the uptake of the prepared nanoparticles by MDA-MB-231 cancer cells (positive CD44 expression) and L929 normal cells (negative CD44 expression). Uptake of the FeO@HA NPs by MDA-MB-231 cells was found to be 4-fold higher than the normal cells. Also, the in vitro analysis showed that, the uptake of FeO@HA NPs by MDA-MB-231 breast cancer cells is significantly enhanced as compared to non-targeted dextran-coated FeO NPs. Moreover, the heat generation capability of the FeO@HA NPs for magnetic hyperthermia application was studied by exposing the prepared nanoparticles to different safe alternating magnetic fields (f = 120 kHz, H = 8, 10, and 12 kA/m). The intrinsic loss power obtained for FeO@HA NPs was about 3.5 nHm/kg, which is about 25-fold larger than that of obtained for commercial available FeO nanoparticles for biomedical applications. Good colloidal stability, biocompatibility, high heating efficacy, and targeting specificity to CD44 receptor-overexpressing cancer cells could make the FeO@HA NPs as a promising multifunctional platform for diagnosis and therapeutic applications.