Interfacial reactions in squeeze cast AC2B Al alloy reinforced with Saffil and Carbon fibers were investigated using scanning and transmission electron microscopy, and secondary ion mass spectrometry. In the case of the as-cast composite, MgO crystals were observed in the vicinity of Saffil fibers. It indicates that the reaction occurred between SiO₂, which was used as a binder to fabricate the preform, and Mg present in the Al alloy during squeeze casting. In the case of T6 treated composite, however, very small MgAl₂O₄ crystals as well as MgO were observed at the surface of the Saffil fibers. Based on SEM and TEM study on the T6 treated composite, the interfacial reactions were observed to occur directly between Al alloy and SiO₂ binder to form both MgO and MgAl₂O₄ crystals. However, a direct reaction between the Al alloy and Saffil fiber were not observed to be significant in T6 treated composite.