Additive manufacturing (AM) technologies have become a target of great industrial interest for manufacture of components and final parts intended for several applications in many sectors of the industry. Most of these components are designed to have a service life higher than 107cycles, making the analysis of the fatigue behavior in the very high cycle regime (VHCF) an essential design criterion. AISI 316L stainless steel is one of the most processed by AM, with numerous approaches in the literature. However, there is still no consolidated knowledge about the behavior of this material when subjected to long or super long fatigue lives after processing by the different available techniques, nor about the predominant crack initiation mechanisms. In general, in the VHCF regime, cracks tend to start internally or in subsurface regions from internal defects present in the material. This fact results in a characteristic in the fracture surface known as fish-eye. Another phenomenon that occurs at the fracture surface, more specifically within the fish-eye region, is the formation of a fine granular area (FGA) nearby the crack initiation sites. The present work analyzed the long-term fatigue strength of AISI 316L steel manufactured by laser directed energy deposition (L-DED) technique. Specimens of two post-processing conditions of the material, with and without heat treatment, were subjected to fatigue tests in ultrasonic equipment (frequency 20 ± 0.5 kHz), with R = -1 aiming 109cycles. After surveying the S-N curves of the two microstructural conditions, the fracture surfaces were analyzed. The research results indicated that the heat treatment reduced the fatigue life of the material as a function of the population of metallurgical defects found, as well as influenced the formation of fish-eye and FGA during the initiation and propagation of cracks. Finally, the size of FGA was experimentally quantified to allow comparison with the dimensions of the FGA estimated by empirical equations present in the literature.