Transmission electron microscopy and energy dispersive X-ray spectroscopy were employed to characterize the composition and crystal structure of ternary Mg–Zn–Ce phase (denoted as T1) in rapidly solidified Mg–6Zn–1Y–1Ce alloy. T1 phase was confirmed having a body-centered orthorhombic structure, which was transformed from the body-centered tetragonal structure Mg 12 Ce phase due to the partial substitution of Mg atoms by Zn. An orientation relationship between T1 phase and matrix was that 〈100〉 T1 || 〈10−10〉 α , 〈010〉 T1 || 〈−12−10〉 α , 〈001〉 T1 || 〈0001〉 α . Under non-equilibrium condition, the contents of Zn and Ce in T1 phase were in the ranges of 28.9–45.3at.% and 7.6–10.4at.%, respectively.