© 2021 Wiley-VCH GmbHCancer remains one of the serious diseases that threaten health, as treatment methods cannot meet the practical needs at the desired level. Therefore, developing new materials that can be used in cancer treatment is an essential effort. The purpose of this study was to develop new materials for boron neutron capture therapy (BNCT) as boron carriers and for photothermal therapy (PTT). Hence, iron borates were prepared with different morphologies and then coated with polydopamine (PDA) to increase the solubility and biocompatibility and also to contribute to the reduction in gold particles. Lastly, gold nanoparticles were deposited on the surface of iron borates, and the photothermal performance of the gold-decorated and PDA-coated iron borates (Fe3BO6@PDA−Au and FeBO3@PDA−Au) was investigated under 808 nm NIR laser. After 900 s irradiation, the temperatures of the dispersions of Fe3BO6@PDA−Au and FeBO3@PDA−Au nanoparticles reached 45.8 and 43.2 °C, respectively. Additionally, the approximate numbers of boron atoms per milligram of Fe3BO6@PDA−Au and FeBO3@PDA−Au nanoparticles were calculated to be 1.23×1018 B mg−1 and 2.79×1018 B mg−1, respectively. In addition to PTT, the functional Fe3BO6@PDA−Au and FeBO3@PDA−Au nanoparticles introduced herein could be helpful in BNCT applications.