The temperature dependence of the elastocaloric effect is studied and the experimental values of the adiabatic temperature change, ΔTad, in the loading/unloading cycles of up to 13.3 K and 16.4 K in quenched and aged Ni50.6Ti49.4 single crystals at 573 K, 1 h, respectively, are obtained. In aged crystals, a specific feature of the elastocaloric effect temperature dependence (an increase in ΔTad above the temperature TR = 273 K) is found, which is due to a change in the sequence of stress-induced martensitic transformation from R–B19' to B2–B19'. The factors (the dissipated energy in the working cycle and the strain hardening coefficient during the stressinduced martensitic transformation) affecting the elastocaloric effect are discussed. It is shown that the aged single crystals have a high coefficient of performance (COP of up to 31), which is promising for the solid-state cooling technologies.