A huge difference between the structure and the properties of equilibrium and metastable Fe–Ga alloys along with an uncertain specification for their metastable state lead to urgent necessity of understanding the cooling rate role in the formation of the alloys structure. We studied structure of Fe-(9-33 at.%)Ga alloys after cooling with different cooling rates (furnace, air, water, as cast) and report structure and dependencies of lattice parameter for A2 and D03 phases on Ga content in Fe–Ga alloys. The first and second critical cooling rates are determined as the beginning and the end of formation of equilibrium L12 phase.