The super duplex stainless steels have a microstructure composed by two phases, ferrite (alpha) and austenite (gamma). This dual microstructure improves simultaneously the mechanical and corrosion resistance properties. However, the welding of these steels is often a critical operation. The present work evaluated the fracture toughness through critical tip open displacement (CTOD) tests of welded joints, with two different heat input, 1.1 kJ mm(-1) and 2.0 kJ mm(-1). The steel used was a super duplex stainless steel (uNs S32750) in presence of hydrogen. The CTOD tests (according BS 7448-1 and BS 7448-2 standards) were performed in air and under different times of hydrogenation. The procedure of hydrogenation has been performed using cathodic potential of -1400 mVscE by 96 and 360 h. The microstructural analysis allowed to determine relevant aspects (alpha/gamma balance, inter austenitic spacing and gamma morphology) and to compare with CTOD results. The results showed strong evidence that the reductions of CTOD values is related to differences in the gamma(2) morphologies. Another important result was the high statistic dispersion in the measures of austenitic spacing, according DNV RP F112-08, which implies in low reliability of using this standard in presence of high anisotropy. The paper also aims to discuss and evaluate which is the best approach to hydrogenated duplex stainless steels: linear elastic fracture mechanics or elasto plastic fracture mechanics. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.