Background: European migrant populations are aging and will increasingly be in need of palliative and end of life care. However, migrant patients are often underrepresented in palliative care research populations. This poses a number of drawbacks, such as the inability to generalize findings or check the appropriateness of care innovations amongst migrant patients. The aim of this study was to develop a self-assessment instrument to help palliative care researchers assess and find ways to improve their projects' diversity responsiveness in light of the aging migrant population, and determine whether in addition to older migrants other groups should be included in the instrument's focus. Methods: After developing a concept instrument based on the standards for equity in healthcare for migrants and other vulnerable groups, literature review and interviews with palliative care researchers, we conducted a Delphi study to establish the content of the self-assessment instrument and used think aloud methods in a study involving seven projects for usability testing of the self-assessment instrument. Results: A Delphi panel of 22 experts responded to a questionnaire consisting of 3 items concerning the target group and 30 items on diversity responsiveness measures. Using an a priori set consensus rate of 75% to include items in the self-assessment instrument, experts reached consensus on 25 out of 30 items on diversity responsiveness measures. Findings furthermore indicate that underserved groups in palliative care other than migrant patients should be included in the instrument's focus. This was stressed by both the experts involved in the Delphi study and the researchers engaged in usability testing. Usability testing additionally provided insights into learnability, error-rate, satisfaction and applicability of the instrument, which were used to revise the self-assessment instrument. Conclusions: The final self-assessment instrument includes a list of 23 diversity responsiveness measures to be taken at varying stages of a project, and targets all groups at risk of being underrepresented. This instrument can be used in palliative care research to assess diversity responsiveness of projects and instigate action for improvement.