The occurrence of magnetization in alloys of the nickel-titanium system is still studied insufficiently. Our early work showed the possibility of magnetization arising during multiple cycles of forward and reverse martensitic transitions in the Ni51Ti49 alloy, as well as after deformation of this alloy by tensile stress to rupture. The purpose of this paper is devoted to revealing the effect of magnetization in samples of the Ni51Ti49 alloy as a result of their single cooling in liquid nitrogen, as well as the disappearance of magnetization when the samples are heated to room temperature. Using an induction hysteresigraph it is found out that the sample has a high magnetization immediately after cooling. As the sample is heated, the hysteresis loops change, acquiring a smaller inclination to the horizontal axis. It indicates a decrease in the magnetic induction to almost zero as the temperature rises to room temperature. The reason for the occurrence and disappearance of magnetization can be associated with micro-deformation processes related to forward and reverse martensitic transitions during cooling and heating of the samples.