Summary: Iron deficiency anaemia (IDA) is a major global public health problem and iron fortification of foods has been recognised as the most cost‐effective prevention strategy. However, traditional iron fortificants are easily oxidised and have poor colloidal stability. Herein, we took advantages of whey protein‐isolated (WPI) amyloid fibrils and developed a stable and effective iron‐WPI fibrils (Fe‐FibWPI) nanocomposite for iron fortification. Compared with native WPI, the antioxidant activity of WPI fibrils was significantly improved after 8 h incubation at 90 °C and pH 2.0. Importantly, the degree of fibrillation and fibril concentration influenced iron reducibility. Therefore, we utilised WPI fibrils as anti‐oxidising nanocarriers to form Fe‐FibWPI nanocomposites. The Fe‐FibWPI showed high dispersibility compared with iron nanoparticles (Fe‐Nano). Further, the in vitro bioavailability of iron was significantly higher in the Fe‐FibWPI at various storage conditions than that in the Fe‐Nano. Moreover, the iron‐WPI fibrils could be processed into liquid, gel and powder forms, which will broaden their application. Fe‐FibWPI nanocomposites have the potential to develop as iron fortificants in IDA management. [ABSTRACT FROM AUTHOR]