Laser Powder Bed Fusion (LPBF) has received an increasing interest over the past few years to produce γ/γ' nickel-based polycrystalline superalloys for high-temperature applications. The first challenge was to make the γ/γ' superalloys processable by modifying their composition, particularly with regard to minor elements (B, Zr, C), these alloys being known to be sensitive to hot cracking. Once the challenge of printability was overcome, other questions emerged. In particular, it has been highlighted that superalloys processed by LPBF often exhibit a drop in ductility in the service temperature range (600 800 °C) that is larger than the one observed in their cast and wrought counterparts. If ones aims at developing the fabrication of superalloys using additive manufacturing, it is essential to quantify this ductility drop and to propose guidelines to control it. In the present work, in collaboration with ONERA and Aubert & Duval, the objective was to clarify the mechanisms responsible for the high temperature ductility loss of the AD730® superalloy. First, subsolvus and supersolvus heat treatments tailored to the LPBF process were developed to control grain size and morphology, as well as to obtain different distributions of γ′ precipitates. High temperature tensile tests (650–800 °C) conducted under air and argon at a strain rate of 10-4 s-1 , revealed a strong that the ductility drop was sensitive to the grain morphology and atmosphere. In particular, the ductility drop was found to be more pronounced under air than under argon. Furthermore, the results show that LPBF-processed AD730® is not necessarily more prone to ductility loss than its conventional cast and wrought counterpart. Fractography analyses, complemented by X-ray tomography and EBSD observations on fractured specimens, revealed the presence of an intergranular damage mechanism at high temperature. TEM and APT analyses of specific regions of interest located at the crack tip were carried out and allowed to identify the mechanisms responsible for this ductility drop. The analyses suggest that the ductility drop is linked to the formation of intergranular oxides. The absence of oxygen segregated at grain boundaries near the crack tip suggests that a Stress Assisted Grain Boundary Oxidation (SAGBO) mechanism is responsible for the ductility drop in polycrystalline nickel-based superalloys during high temperature tensile loading.