A multifunctional nanotheranostic agent was developed by conjugating both hyaluronic acid and bovine serum albumin coated CuInS 2-ZnS quantum dots onto the surface of magnetic Prussian blue nanoparticles. The obtained nanoagent could serve as an efficient contrast agent to simultaneously enhance near infrared (NIR) fluorescence and magnetic resonance (MR) imaging greatly. The coexistence of magnetic core and CD44 ligand hyaluronic acid was found to largely improve the specific uptake of the nanoagent by CD44 overexpressed HeLa cells upon applying an external magnetic field. Both NIR fluorescence and MR imaging in vivo proved high accumulation of the nanoagent at tumor site due to its excellent CD44 receptor/magnetic dual targeting capability. After intravenous injection of the nanoagent and treatment of external magnetic field, the tumor in nude mice was efficiently ablated upon NIR laser irradiation and the tumor growth inhibition was more than 89.95%. Such nanotheranostic agent is of crucial importance for accurately identifying the size and location of the tumor before therapy, monitoring the photothermal treatment procedure in real-time during therapy, assessing the effectiveness after therapy.