Objectives: Internationally, funders require stakeholder involvement throughout health technology assessment (HTA). We report successes, challenges, and lessons learned from extensive stakeholder involvement throughout a palliative care case study that demonstrates new concepts and methods for HTA.Methods: A 5-step “INTEGRATE-HTA Model” developed within the INTEGRATE-HTA project guided the case study. Using convenience or purposive sampling or directly / indirectly identifying and approaching individuals / groups, stakeholders participated in qualitative research or consultation meetings. During scoping, 132 stakeholders, aged ≥ 18 years in seven countries (England, Italy, Germany, The Netherlands, Norway, Lithuania, and Poland), highlighted key issues in palliative care that assisted identification of the intervention and comparator. Subsequently stakeholders in four countries participated in face–face, telephone and / or video Skype meetings to inform evidence collection and / or review assessment results. An applicability assessment to identify contextual and implementation barriers and enablers for the case study findings involved twelve professionals in the three countries. Finally, thirteen stakeholders participated in a mock decision-making meeting in England.Results: Views about the best methods of stakeholder involvement vary internationally. Stakeholders make valuable contributions in all stages of HTA; assisting decision making about interventions, comparators, research questions; providing evidence and insights into findings, gap analyses and applicability assessments. Key challenges exist regarding inclusivity, time, and resource use.Conclusion: Stakeholder involvement is feasible and worthwhile throughout HTA, sometimes providing unique insights. Various methods can be used to include stakeholders, although challenges exist. Recognition of stakeholder expertise and further guidance about stakeholder consultation methods is needed.