Breast cancer is the deadliest cancer among women and its treatment using traditional methods leads the patient to experience adverse effects. However, photodynamic therapy (PDT) is a non-invasive therapy modality that works through a photosensitizing agent, which treating activated by a suitable light source, releases reactive oxygen species capable of treating cancer. Furthermore, recent research indicates that combining PDT and nanoparticles can enhance therapeutic effects. In this way, the synthesis of IONPs (iron oxide nanoparticles) was carried out, and their subsequent coating was done with curcumin (IONPs@curcumin) so that they could act as therapeutic agents against breast cancer. Curcumin solubility tests were carried out to achieve the best results, with ethanol as a solvent, in different concentrations of ethanolic curcumin solution, with the optimal outcome observed at a concentration of 1 mM. Subsequently, the stability analysis was conducted by adjusting the pH of the medium, revealing that at pH 10, the IONPs@curcumin exhibited the best stability and dispersion conditions. Then, cytotoxicity tests of IONPs@curcumin were carried out on the MDA-MB-468 triple-negative breast cancer cell line, under experimental conditions without irradiation and subjected to PDT. The results revealed a viability greater than 70%, as it did not exhibit cytotoxicity for cells in the dark. After 1 h of incubation, the PDT associated with IONPs@curcumin showed 32% of cell viability at a concentration of 30 mg/mL.