In this work, a multifunctional theranostic nanocomposite based on CoFe 2 O 4 @polyacrylic acid (PAA)-Folic Acid (FA) Doxorubicin (Dox) load NPs was designed for the multifunctional cancer treatment. Several techniques such as TEM, DLS, ζ -potential, vibrating sample magnetometer, XRD, and UV-Vis spectrophotometer were applied for investigating physicochemical properties of the nanosystem. The percentage of the loaded drug, loading efficiency, in vitro release (pH 5.4 and 7.4), in vitro MRI measurements, and MTT assay (4T1 and 9A9 cell lines) were evaluated. Results showed that the percentage of loaded drug and loading efficiency was 53.33 ± 3.5 and 80.00 ± 5.3%, respectively, showing the system's high ability for Dox encapsulation. Release study showed that Dox loaded in the CoFe 2 O 4 @PAA-FA(Dox) load NPs released faster at pH 5.4 than pH 7.4. In vitro , MRI measurements confirmed that CoFe 2 O 4 @PAA NPs could be used as a contrast agent in MRI measurements with r 2 = 18.2 mM -1 s -1 . MTT assay demonstrated the biocompatibility of NPs, also showed a more efficient therapeutic effect for CoFe 2 O 4 @PAA-FA(Dox) load NPs than free Dox and CoFe 2 O 4 @PAA(Dox) load NPs., (© 2021 IOP Publishing Ltd.)