A small number of research studies have found that mindfulness helps to reduce symptoms of depression, anxiety, and rumination in people who are autistic. However, there has been little qualitative research about the experience of autistic adults who practice mindfulness and other contemplative practices. In addition, we don’t yet know if the questionnaires that are used to measure the effects of mindfulness practice are suitable for autistic adults. Our aim is to find out more about the experiences, preferences, and challenges experienced by autistic adults who engage in mindfulness and related practices, and to determine whether existing mindfulness outcome questionnaires are suitable. We will arrange discussion groups and an online survey for autistic adults to find out about their experiences. We will discuss some of the existing mindfulness outcome questionnaires with mindfulness teachers, researchers, and autistic adults, and if they don’t appear suitable we will discuss what questions should be asked and how the questionnaires should ask them. Our findings will help to ensure that mindfulness practices can be appropriately tailored to meet the needs of autistic adults, reducing the likelihood of adverse effects, and identify items for a new mindfulness outcome questionnaire, if a new questionnaire is needed.