Laser powder bed fusion (LPBF) is one of the most attractive metal additive manufacturing technologies, receiving growing attention for the fabrication of parts without geometrical complexity restrictions linked to the layer by layer fabrication method. The production of metal components by LPBF usually yield comparable and sometimes superior mechanical properties compared to those of bulk materials, in terms of strength and ductility of the as-built parts. One of the major drawback given by using LPBF process refers to the tendency to produce undesirable microstructural defects, such pores, with various shapes and morphology, and inclusions. These must be minimized and reduced in extension since they strongly affect the performance of the manufactured components. The AISI 316L austenitic stainless steel is one of the most widely produced metallic materials owing to its excellent properties such as corrosion resistance, high ductility, and biocompatibility, very promising for structural and biomedical application. In the present work, microstructure, defect formation and mechanical properties of AISI 316L stainless steel components fabricated by LPBF are investigated and compared to bulk parent steel. Both printed and bulk components were subjected to post-processing homogenization heat treatment to investigate its effect on the mechanical and microstructural behaviour of 316L SS. Thence, the heat treatment was performed at 1150 °C for a dwell time of 2 hours, followed by furnace cooling. Samples were then cut to XY plane (parallel to the printing plate) and to YZ plane (the growth direction). Optical microscopy inspections were carried out to detect fabrication defects and to allow the quantification of porosity. Chemical etching was also performed to highlight the microstructure of the samples and additional investigations using also scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were performed. Both hardness and micro-hardness tests were used to evaluate the mechanical performance of the material. Finally, X-Ray Diffraction (XRD) was carried out to quantitatively determine the distribution of crystallographic phases of the as built and heat-treated samples. The experimental results revealed that heat treatment leads to significant modifications of the material properties and performance.