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In high-temperature applications, like exhaust manifolds, cast irons with a ferritic matrix are mostly used. However, the increasing de-mand for higher-temperature applications has led manufacturers to use additional expensive materials such as stainless steels and Ni-resist austen-itic ductile cast irons. Thus, in order to meet the demand while using low-cost materials, new alloys with improved high-temperature strength and oxidation resistance must be developed. In this study, thermodynamic calculations with Thermo-Calc software were applied to study a novel ductile cast iron with a composition of 3.5wt％ C, 4wt％ Si, 1wt％ Nb, 0–4wt％ Al. The designed compositions were cast, and thermal analysis and microstructural characterization were performed to validate the calculations. The lowest critical temperature of austenite to pearlite eutectoid transformation, i.e., A1, was calculated, and the solidification sequence was determined. Both calculations and experimental data revealed the im-portance of aluminum addition, as the A1 increased by increasing the aluminum content in the alloys, indicating the possibility of utilizing the al-loys at higher temperature. The experimental data validated the transformation temperature during solidification and at the solid state and con-firmed the equilibrium phases at room temperature as ferrite, graphite, and MC-type carbides.