Although metal additive manufacturing has been widely studied owing to its flexible product shape design, the material selection window for metal additive manufacturing remains narrow owing to limited feedstocks. To address the challenges in additive manufacturing, an innovative metal powder fabrication process was developed in this study. This process is known as surface modification and reinforcement transplantation (SMART), and it efficiently produces surface-modified feedstock powders, such as spheroidized, surface-alloyed, surface-coated, or composite powders, which facilitate the exploration of new alloys and composites via additive manufacturing. In this study, the working principles of the SMART process were established, and some practical applications of the SMART process were considered by fabricating specialized metal additive manufacturing feedstocks such as carbon nanotube-coated, Mo alloyed, and TiC particle-reinforced Inconel 625 powders. Furthermore, Mo-alloyed and TiC particle-reinforced powders were utilized in the directed energy deposition process to validate the performance of the SMART powder by fabricating Mo-controlled alloy and TiC particle-reinforced composites. The SMART process was compared with the existing processes and proved to be advantageous. Therefore, this study provides a novel method for producing feedstock powders for additive manufacturing.