BackgroundMental healthcare users and patients were described as a particularly vulnerable group in the debate on the burdens of the COVID-19 pandemic. Just what this means and what normative conclusions can be derived from it depend to a large extent on the underlying concept of vulnerability. While a traditional understanding locates vulnerability in the characteristics of social groups, a situational and dynamic approach considers how social structures produce vulnerable social positions. The situation of users and patients in different psychosocial settings during the COVID-19 pandemic has not yet been comprehensively considered and ethically analyzed under the aspect of situational vulnerability.MethodsWe present the results of a retrospective qualitative analysis of a survey of ethical challenges in different mental healthcare facilities of a large regional mental healthcare provider in Germany. We evaluate them ethically using a dynamic and situational understanding of vulnerability.ResultsDifficulties in implementing infection prevention measures, restrictions of mental health services in favor of infection prevention, social isolation, negative health effects on mental healthcare users and patients, and challenges in implementing regulations on state and provider levels within the local specificities emerged across different mental healthcare settings as ethically salient topics.ConclusionsApplying a situational and dynamic understanding of vulnerability allows the identification of specific factors and conditions that have contributed to an increased context-dependent vulnerability for mental healthcare users and patients. These factors and conditions should be considered on the level of state and local regulations to reduce and address vulnerability.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12910-023-00910-3.