Purpose - This paper aims to identify conditions affecting sustainability of Lean implementations in Swedish psychiatric healthcare, from a socio-technical perspective. Design/methodology/approach - Longitudinal focus group interviews were conducted with 24 first-line managers within Swedish psychiatric healthcare. The analysis was made using Cherns ten socio-technical principles and a framework for sustainable development work in healthcare. Findings - The most critical socio-technical principles for a sustainable Lean implementation were boundary location; power and authority; and compatibility. At hospital level, socio-technical principles were inhibited by the weak ownership of the Lean implementation. However, strong ownership at division level meant the same principles were supported. Unclear goals made follow-ups difficult which had negative effects on the learning processes in the Lean implementation. The role and responsibility of first-line managers were unclear in that they perceived they lacked power and authority resulting in negative effects on the participation - an important sustainability concept. Originality/value - Empirically based papers assessing Lean implementations in psychiatry are rare. This study is a contribution to the research area of sustainable Lean implementations in healthcare. The practical implication of this study is that decision makers, senior managers, first-line managers and psychiatrists can be supported in reaching sustainable implementations of Lean.