Extensive debate surrounds the practice of palliative sedation (PS, i.e. sedative drugs to lower consciousness in patients nearing death), particularly given reports of improper application, suboptimal performance and poor communication. Initiatives undertaken to date to evaluate and improve PS were focused on a single outcome domain unlikely to reflect overall sedation quality and thus, leading to an incomplete evaluation of the overall PS practice. In order to monitor and improve the practice, this project will develop, operationalize and validate an agreed standardized core outcome set (COS) for the evaluation of palliative sedation in clinical research and practice. We will 1) identify relevant outcomes by means of a systematic review and 20 semi-structured interviews; 2) prioritize these outcomes by multiple stakeholders and achieve convergence on their importance using the Delphi technique resulting in the COS; 3) identify outcome measurement instruments for all included outcomes in the COS through a systematic review; 4) determine how the outcomes should be measured through consensus meetings with representative stakeholders; and 5) assess validity and reliability of the COS through field-testing. This project is a necessary step to develop a gold-standard measurement instrument that can evaluate the overall practice of PS, and which would facilitate the design and evaluation of clinical trials and audits.