<p>The enhancement of high-temperature properties can significantly expand the industrial applications of aluminum alloys. This study investigates the influence of Fe and Ni content and thermal exposure on the high-temperature mechanical properties of hypereutectic Al–Si–Cu–Mg alloys. The results show that the volume fraction of the T-Al₉FeNi phase increases with the rising Fe and Ni content, enhancing the connectivity of the high-temperature-resistant multiphase network skeleton. This improvement leads to an increase in tensile strength at 250&#xa0;°C from 192 to 241 MPa, corresponding to a 25.5% enhancement. Simultaneously, the increased Fe and Ni content causes the T-Al₉FeNi phase size to grow from 2.48 ± 0.1 to 3.07 ± 0.05 μm. The larger T-Al₉FeNi phase size promotes crack propagation, resulting in a reduction in elongation from 2.3 to 1.4%. After thermal exposure at 400 °C for 100 h, the secondary phase undergoes dissolution and spheroidization, reducing the connectivity of the high-temperature-resistant multiphase network skeleton. Consequently, the tensile strength of the Al–Si–Cu–Mg alloy decreases at both room temperature and 250 °C, while elongation improves. Furthermore, the T-Al₉FeNi phase exhibits relatively excellent thermal stability at 400 °C.</p>