Metal parts are currently being fabricated using 3D metal printing technology. One of the most prevalent and precise techniques is selective laser melting (SLM), which uses metallic powder as the material injected into the laser. This study focuses on the effect of heat treatment on the Inconel 718 printed parts in the case of porosity and heat treatment. Porosity was investigated by using the computer analysis method and showed that the heat treatment reduced porosity by 67% (from 0.056 to 0.018%) for the section perpendicular to the printing plane. For sections parallel to the printing plane, the average porosity reduced by 76% (from 0.134 to 0.031%). Heat treatment markedly improved the microstructure of SLM Inconel 718 by refining the grain structure and removing detrimental Laves phases. These enhancements result in enhanced mechanical properties, rendering the material more appropriate for high-performance applications.