The effect produced by the rate of heating to the aging temperature of 500°C on the character of phase transitions, the formation of a phase-structure state, and the change in hardness in the quenched Ti–10V–2Fe–3Al titanium alloy with different carbon contents has been studied by differential scanning calorimetry (DSC), scanning electron microscopy, X-ray diffraction analysis, and durometry. It has been shown that the change in the heating rate and carbon content of the alloy has an effect on the temperatures of the exothermic peaks of phase transitions associated with that the metastable solid β-solution formed under quenching decomposes in the process of heating. It has been established that a decrease in the rate of heating to the aging temperature from 40 to 10°C/min and an increase in the carbon content from 0.008 to 0.034 wt % in the quenched Ti–10V–2Fe–3Al alloy improves the dispersity of secondary phases formed after quenching and thereby promotes a growth in the alloy hardness. The effect of the heating rate and carbon content on the change in the parameters calculated by the full-profile analysis of X-ray diffraction pattern for the phases detected after treatment is considered.