<p>Recently, wire arc additive manufacturing (WAAM) has been widely investigated for the fabrication of large-dimensional components in industries. Due to the principle of layer manufacturing in WAAM, the deposited material is subject to complex thermal cycles, which strongly impact microstructures and mechanical properties of components. To provide an insight into such effects, in this paper, the thermal cycles during the cold metal transfer (CMT)-WAAM process of an Inconel 625 rectangular wall are first analyzed. Subsequently, the relationship between thermal cycles and metallurgical properties of the as-deposited wall is explored. For these purposes, numerical models were developed to simulate the thermal behavior during the deposition process. Experimental tests, including microstructure and phase characterization, microhardness, and tensile tests were carried out. The results reveal that WAAM involves repeated thermal cycles with rapid heating rates and slow cooling rates, leading to a dynamic temperature profile. Due to heat accumulation phenomenon along deposited layers, the microstructure of the as-deposited material consists of columnar dendrites with the spacing between dendrite arms increasing as the build height rises. Mechanical properties, including microhardness and tensile strength, correlate with the microstructural variation, with the bottom region showing the finest microstructure and the highest mechanical strength. In contrast, the upper region exhibits coarser grains and reduced microhardness and tensile strengths. These findings highlight the significant role of thermal cycles in determining both the microstructure and mechanical performance of an Inconel 625 thin wall fabricated by CMT-WAAM.</p>