Background: Little is known about how to involve people with intellectual disabilities in making decisions about treatment and care in their palliative phase. We aimed to reach a consensus about a shared decision-making (SDM) conversation aid for people with intellectual disabilities, relatives, and healthcare professionals. Methods: In a Delphi process, an expert panel of 11 people with intellectual disabilities, 14 relatives, and 65 healthcare professionals completed online questionnaires about the relevance and feasibility of a draft conversation aid. Results: In Round 1, components were rated as (very) relevant by 70-98% of participants (M = 87%). In Round 2, after amending the aid in response to feedback, relevance ratings were 67-97% (M = 90%) and feasibility ratings 66-86% (M = 77%). The final version consists of four themes: who are you; illness/end-of-life; making decisions; and evaluating the decision. Conclusion: The consensus-based conversation aid is considered sufficiently relevant and feasible to be implemented in practice.