The $\alpha \rightarrow \gamma$ recrystallization of carbon-supersaturated ferrite alloyed with $\alpha$-stabilizer is analysed. The $\alpha$-stabilizer is redistributed between austenite and ferrite by recrystallization. A plane front of recrystallization becomes unstable and is transformed into cellular or dendrite one. The perturbation method, which is developed by W. W. Mullins and R. F. Sekerka for crystallizing alloys, is used in the analysis. A sinusoidal perturbation with infinitesimal amplitude is introduced into a plane front of recrystallization. The rate of movement of each element of the interphase surface is calculated by means of the diffusion flow of carbon from the austenite and by the flow of $\alpha$-stabilizer into the ferrite. The velocities are equated, and an expression for the change of perturbation amplitude is obtained. The most significant factors influencing on the stability of the $\alpha \rightarrow \gamma$ plane front of recrystallization are as follow: the difference in concentrations of $\alpha$-stabilizer in ferrite and austenite at the interface, the average velocity of front, the diffusion coefficient of the $\alpha$-stabilizer in ferrite, the coefficient of the interface tension. All factors depend on temperature. Therefore, the significance of factors can vary with temperature changes. The example of Fe–Si–C alloys shows the correspondence of the theoretical and experimental results of the study. The possibility of applying the obtained results to describing the $\alpha \rightarrow \gamma$ + carbide cooperative transformation in ferritic iron alloys with carbide-forming elements during carburizing is shown.