The paper describes the improvement of the technology for the production of gas turbine engine (GTE) blades made of heat-resistant nickel-based alloys by modifying Hf and Zr and optimizing the heat treatment regime. The introduction of modifiers reduced the average macrograin size, the number and size of the brittle component in the form of facets of intragranular cleavage, the size of dendritic cells, and the distance between the axes of second-order dendrites. Modification led to the breaking of the branches of the MC-based “Chinese-script” eutectic and their spheroidizing, resulting in structure refinement and increase in the amount of the eutectic (γ + γ′)-phase, thus enhancing the γ′-phase strengthening of the heat-treated blades. Adding 0.03–0.05 wt.% Zr and heat treatment at 1230 ± 5 °C resulted in increase in tensile strength by 5%, the elongation by 1.5 times, the impact toughness by 1.3 times, the long-term strength at 975 °C and 760 °C—by 1.8 times and 2.7 times respectively. Simultaneously adding 0.03–0.06 wt.% Zr and 0.4–0.7 wt.% Hf improved the tensile strength by 7%, the elongation by 50%, the impact toughness by 100%, and the long-term strength at 850 °C by 20%. The enhanced mechanical properties of modified heat-resistant Ni-based alloys benefit the service life and exploitation reliability of gas turbine engines.