The results of theoretical and experimental studies of the phase transformations features in the multicomponent aluminium casting alloy AK5M2 with iron content from 0.83 to 3.3% are presented. The Thermo-Calc software and database COST2 were used to simulate the phase transformations, and to calculate the phase precipitations and their mass fraction during the equilibrium and non-equilibrium (Scheil–Gulliver module) solidification interval of the alloys at the defined compositions. Different thermo-analytical techniques were used to determine the undercooling at the beginning of the solidification and phase transformations temperatures: Computer Aided Cooling Curve Analysis (CA-CCA), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). As shown, that computer thermodynamic simulation of phase transformations is an effective tool to predict the phase composition of the casting alloys and to interpretate the results of thermal analysis and ensures the accuracy of the obtained information. The combined usage of these methods made it possible to establish that the increase of iron content leads to the decrease of nucleation undercooling and to increase of the solidus–liquidus temperature range for studied alloys and an increase in the amount of an iron-bearing inter-metallic compound, as well as to a change in the order and mechanism of their formation. The phase precipitations of the AK5M2 alloy with 0.83% Fe begin with formation of the primary (Al) phase in the melt. Iron content increase in the alloy up to 1.46% Fe leads to the precipitation Al$_{8}$Fe$_{2}$Si ($\alpha$) phase. In the 2.0% Fe alloy, there is primary phase Al$_{13}$Fe$_{4}$. However, at both concentrations of iron (1.46% and 2.0%), the volume fraction of these primary phases is insignificant. Increasement of iron content up to 3.3% Fe, the same as for the alloy with 2% Fe, two iron-bearing intermetallic Al$_{13}$Fe$_{4}$ and Al$_{8}$Fe$_{2}$Si ($\alpha$) precipitate primarily from the melt, the first is formed with significant thermal effect. Regardless of iron content in the alloy, the maximum amount of Fe-bearing intermetallics Al$_{5}$FeSi ($\beta$), Al$_{15}$(Fe, Mn)$_{3}$Si$_{2}$, Al$_{8}$Fe$_{2}$Si ($\alpha$) are precipitate during eutectic reactions after the primary crystals of aluminium (Al). The processes of intermetallic compounds Mg$_{2}$Si and Al$_{2}$Cu($\theta$) formation occurs at the last stages of solidification, and practically not depend from the concentration of iron in the alloy.