Austenite–ferrite transformation at different isothermal temperatures in low carbon steel was investigated by a two-dimensional cellular automaton approach, which provides a simple solution for the difficult moving boundary problem that governs the ferrite grain growth. In this paper, a classical model for ferrite nucleation at austenite grain boundaries is adopted, and the kinetics of ferrite grain growth is numerically resolved by coupling carbon diffusion process in austenite and austenite–ferrite (γ–α) interface dynamics. The simulated morphology of ferrite grains shows that the γ–α interface is stable. In this cellular automaton model, the γ–α interface mobility and carbon diffusion rate at austenite grain boundaries are assumed to be higher than those in austenite grain interiors. This has influence on the morphology of ferrite grains. Finally, the modeled ferrite transformation kinetics at different isothermal temperatures is compared with the experiments in the literature and the grid size effects of simulated results are investigated by changing the cell length of cellular automaton model in a set of calculations.