In this study, laser metal deposition (LMD) additive manufacturing was used to deposit the pure Inconel 625 alloy and the TiC/Inconel 625 composites with different starting sizes of TiC particles, respectively. The influence of the additive TiC particle and its original size on the constitutional phases, microstructural features, and mechanical properties of the LMD-processed parts was studied. The incorporation of TiC particles significantly changed the prominent texture of Ni–Cr matrix phase from (200) to (100). The bottom and side parts of each deposited track showed mostly the columnar dendrites, while the cellular dendrites were prevailing in the microstructure of the central zone of the deposited track. As the nano-TiC particles were added, more columnar dendrites were observed in the solidified molten pool. The incorporation of nano-TiC particles induced the formation of the significantly refined columnar dendrites with the secondary dendrite arms developed considerably well. With the micro-TiC particles added, the columnar dendrites were relatively coarsened and highly degenerated, with the secondary dendrite growth being entirely suppressed. The cellular dendrites were obviously refined by the additive TiC particles. When the nano-TiC particles were added to reinforce the Inconel 625, the significantly improved microhardness, tensile property, and wear property were obtained without sacrificing the ductility of the composites.