The effect of Si on Fe-rich intermetallic formation and the mechanical properties of the heat-treated squeeze cast Al–5.0Cu–0.6Mn–0.7Fe alloy was investigated. Our results show that increasing the Si content promotes the formation of Al15(FeMn)3(SiCu)2 (α-Fe) and varies the morphology of T (Al20Cu3Mn2), where the size decreases and the amount increases. The major reason is that Si promotes heterogeneous nucleation of the intermetallics leading to finer precipitates. Si addition significantly enhances the ultimate tensile strength and yield strength of the alloys. The strengthening effect is mainly owing to the dispersoid strengthening by increasing the volume fraction of the T phase and less harmful α-Fe with a compact structure, which makes it more difficult for the cracks to initiate and propagate during tensile test. The squeeze cast Al–5.0Cu–0.6Mn–0.7Fe alloy with 1.1% Si shows significantly improved mechanical properties than the alloy without Si addition, which has a tensile strength of 386 MPa, yield strength of 280 MPa, and elongation of 8.6%.