Abstract: Slag foaming is an important operation in electric arc furnace steelmaking, and modern steel shops worldwide currently apply this practice. However, an efficient slag-foaming practice requires not only control of the process variables at the industrial scale but also a fundamental understanding of the foaming phenomena, which can be achieved through the development of mathematical models. However, research in this field is lacking owing to the extreme complexity of slag foaming. In this work, a three-dimensional computational fluid dynamics model was developed based on the coupled Euler–Euler multiphase flow and population balance models. The model predicted the foam height and foaming index. It was validated against experimental data for batch smelting slags containing CaO–SiO₂–Al₂O₃–FeO at 1773 K under a constant slag basicity, with the relative error in the foaming index being less than 1.4%. When applied to steelmaking slags, the model accurately reproduced slag foaming. The model predictions indicated that increasing the FeO content from 3wt% to 30wt% decreased the foaming index from approximately 1.3 to 0.5.