Despite its superior corrosion resistance, super duplex stainless steels (SDSS) are prone to hydrogen embrittlement. In this paper, a novel in situ electrochemical nanoindentation technique is used to investigate the hydrogen effect on the nanomechanical response of the existing phases in SDSS, i.e. ferrite and austenite. A systematic change in electrochemical (EC) charging potential revealed the interconnected nature of the hydrogen effect on the nanomechanical properties of SDSS. It is shown that the hydrogen effects in each phase are very different and are strongly coupled with the existing residual stresses in the microstructure induced during the manufacturing and/or induced by EC hydrogen charging. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.