<p>The directed energy deposition (DED) process is a highly effective technique for repair, remanufacturing, and enhancing properties of metallic parts. However, defects that appear in the DED process impeded the advancement of this technology. In order to minimize defects, thermo-mechanical characteristics of the process should be understood. The goal of this study is to investigate thermo-mechanical characteristics of thin-wall shapes with different lengths fabricated by DED using a three-dimensional (3D) finite element analysis (FEA). The shape errors observed according to the deposition length were compared with the results of experiments. The FEA model was validated through experimental and analytical methods, considering heat flux efficiency, convection coefficient, and heat sink coefficient. The influence of the molten pool on shape deviations was examined through the temperature distribution. The residual stress distribution was estimated based on the yield strength of the 17-4PH martensitic phase. Thermo-mechanical properties were analyzed by comparing the thermal and stress histories corresponding to different deposition lengths.</p>