<p>Solid oxide electrolyzer cells (SOECs) contain many critical and/or strategic elements such as Co, Mn, Ni, Sr and rare earth elements (Ce, Gd, La). To achieve a circular economy, an efficient recycling process needs to be developed. For electrolyte-supported cells, no mechanical separation processes come into question because of their brittle construction. Hence, a hydrometallurgical approach was chosen in this work, starting with a leaching process of grinded membrane electrode assemblies from spent SOECs. Different leaching reagents (H₂SO₄, HNO₃, HCl, citric acid, ammonia solution) with and without additives (Na₂SO₃, H₂O₂), which potentially support the reduction and thus the dissolution of higher oxides present, were tested. The best conditions were further investigated, resulting in an optimal leaching process using 4.5&#xa0;M hydrochloric acid without the addition of any reducing agent at 60&#xa0;°C for 2.5&#xa0;h. The elements of the electrolyte (Hf, Zr, Y) were not leached under these conditions. Leaching efficiencies over 89% could be reached for all leached elements except Gd (leaching efficiency of at least 81%). Hence, an electrolyte separation is possible through this leaching process and both material flows (electrolyte residue and leaching solution) can be handled separately in further recycling steps.</p> Graphical Abstract <p></p>