Abstract <p>The heat capacity of the AlBe1 aluminum alloy (Al + 1 wt % Be) with magnesium additives in the cooling mode has been determined using the known heat capacity of a copper reference sample. Processing the cooling rate curves of samples of AlBe1 alloy with magnesium and the reference (Cu grade M00) resulted in deriving equations to describe the temperature dependence of the cooling rate. Based on the experimental finding the cooling rates of alloy samples and the reference and knowing the sample mass the polynomials of the temperature dependence of the heat capacity have been determined. The polynomials are described using a four-term equation. The integrals of the specific heat capacity allow one to find the temperature dependencies of the change in enthalpy, entropy, and the Gibbs energy for the AlBe1 aluminum alloy containing magnesium. Using the polynomial dependencies we obtained, it is shown that with increasing temperature the heat capacity, enthalpy, and entropy increase in alloys, whereas the Gibbs energy decreases. Adding magnesium in the studied concentration range (0.05–1.0 wt %) leads to an increase in the heat capacity, enthalpy, and entropy in the initial AlBe1 alloy, while the Gibbs energy decreases.</p>