In this research, we synthesized a novel caffeic acid-functionalized iron oxide nanoparticles (CFA-functionalized SPION) L929 (mouse fibroblast cell), U87 (glioblastoma brain cancer cell), MCF-7 (breast cancer cell), HeLa (cervix cancer cell), and A549 (human lung cancer cell) cell lines. Thermal decomposition and Stober methods were used to prepare APTES-capped SPION, respectively. The carboxylated polyethylene glycol (PEG-COOH), folic acid (FA), and caffeic acid (CFA) were attached to the surface of SPION via carboxylic/amine groups. Structural analysis (Rietveld analysis) confirmed the phase purity of the product. The conjugation of organics to the surface of SPION was followed with FT-IR spectroscopy and thermal gravimetric analysis (TGA). SEM analysis presented the spherical morphology of product with 13 +/- 3 nm particle size. And also, superparamagnetic property of product was deduced from VSM analysis. Uptake of CFA-functionalized SPION from the cell and release of CFA from CFA-functionalized SPION has been studied by using Prussian blue staining and spectrophotometer, respectively. Also, cell viability and cytotoxicity was tested by MTT and LDH assays. The uptake of CFA-functionalized SPION by HeLa, MCF-7, and U87 was higher than A549 and L929 cells. Also, caffeic acid release from CFA-functionalized SPION increased at an acidic environment (pH 4.4). A newly synthesized CFA-functionalized SPION in all used concentrations decreased cell viability and increased cytotoxicity at 24th and 48th hours. The results showed that the CFA-functionalized SPION is a potential anticancer agent for cancer therapy.