In this work, MIG process was utilized for the wire arc additive manufacturing of the wall-shaped parts, using NiTi shape-memory alloy. High-scale specimens consisting of 20 layers were deposited by using Ni-rich (Ni55.56Ti wt.%) wire as a feedstock on the NiTi substrate with the identical chemical composition. One of two specimens was heat-treated at a temperature of 430 °C for 1 h. The influence of such a heat treatment on the microstructure, phase transformation temperatures, chemical and phase compositions, microhardness, and tensile and bending tests’ results is discussed. As-deposited metal successfully demonstrates superelastic behavior, except in the lower zone. In regard to the shape-memory effect, it was concluded that both the as-deposited and the heat-treated samples deformed in liquid nitrogen completely restored (100%) their shapes at an initial strain of 4–5%. An occurrence of the R-phase was found in both the as-deposited and the heat-treated specimens. The phase transformation temperatures, microstructure, and tensile and bending tests results were found to be anisotropic along the height of the specimens. The presented heat treatment led to changes in the functional and mechanical properties of the specimen, provided with the formation of finely dispersed Ni4Ti3, NiTi2, and Ni3Ti phases.