Apart from many governing parameters, the interfacial heat transfer coefficient (IHTC) has prime importance for the numerical simulation of casting as it quantifies the heat flux between casting and mold (or chill). Most Mg alloys are based on the Mg-Al system and casting is the commonly used production process. The experimental configuration makes it challenging to measure flux and surface temperatures required to evaluate the IHTC. In this study, the IHTC was predicted for a variety of Mg-Al compositions which were cast using a permanent cylindrical mold. Unidirectional heat flow was ensured in order to replicate the experimental conditions for solving the one-dimensional transient heat equation. The numerically determined mold and surface temperatures, using Beck's inverse methodology, were in good agreement with the experiments and analytical solution, respectively. Moreover, the heat transfer behavior across the interface depicted in the form of IHTC was analyzed, also various empirical and numerical aspects of the method are discussed.