The '1+ Million Genomes' (1+MG) initiative, coordinated by the Beyond 1 Million Genomes (B1MG) project, aims to enable secure access to genomic and corresponding clinical data across Europe for research, personalised healthcare, and policy making. It is a joint initiative of 24 EU countries, the UK, and Norway. Citizen engagement and public trust have been raised as critical components in the B1MG stakeholder forum meetings and country visits. To discuss these components, an online expert workshop was facilitated on January 18, 2023. 14 Participants were invited to give a short presentation on their lessons learned regarding citizen engagement. They were selected for their expertise in bioethics, ELSI, governance, human genetics, patient representation and citizen engagement. After discussion they formulated recommendations to participating 1+MG countries. Lessons learned from various engagement activities were shared under three subthemes: “When an ELSI framework is in place, what is the (additional) role of citizen engagement in fostering data sharing and public trust?”; “How does citizen engagement relate to (interests of) other stakeholders?”; “When and how to engage and at what level?”. It was discussed that citizen engagement can have a diversity of aims that may help create preconditions for accountable research and trust. ELSI or trustworthiness frameworks don’t necessarily lead to participants having trust in an institution. The addition of citizen engagement can help build and contribute to trust. Engagement activities are situated in context with potentially conflicting interests, power differences and priorities, for instance between publicly accountable researchers and private companies. While data sharing involves international collaboration, trust is relational and context specific and dependent on many factors including the relation to the professionals or institutions asking for data sharing and trust. The tools used for citizen engagement vary for different contexts and goals. If engagement starts at the beginning of a project, there are more options to influence choices and policies. Recommendations (See D1.7) stress the need for dedicated resources; acknowledging different views and interests; the need for capacity building to enable engagement; creating meaningful participation via selected tools through early engagement with a careful choice of engagement strategy; having good and transparent governance for enabling trustworthiness to contribute to accountability; and the need to find ways to connect the relational trust established at the national level to the EU level. Health care professionals and professional organisations, particularly in the field of medical genetics, can play an important part in informing and engaging with citizens and patients and building trust. Citizen engagement needs sustained resources and attention across projects and national and EU initiatives. Trust depends on citizens and patients, so a trustworthy data sharing infrastructure needs transparent governance to consider and incorporate citizen views.