Open data has been promoted as a tool to improve the transparency, robustness, and efficiency of scientific research. However, the perspectives of participant communities, particularly those who are marginalised, are often overlooked in discussions around open data. This paper examines, for the first time, the views of autistic adults and parents of autistic people regarding open data practices in autism research. Thirty interviews were conducted, which considered participants’ views on different degrees of openness of research data, and the factors that would influence their level of comfort with their and/or their child’s data being shared. Pre-registered reflexive thematic analysis that interrogated power dynamics in the participants’ statements led to the development of two themes: (1) Narratives of, and created by, Research, and (2) Vulnerability and Risk in Research Participation. These themes reflected how the impacts of open data were experienced both individually and collectively. Participants acknowledged the potential benefits of open data for knowledge generation and improving services, but also expressed concerns about misuse, re-identification, and harmful narratives from secondary researchers that they had not engaged with. The findings highlight the importance of meaningful engagement with participant communities to ensure ethical and transparent open data practices, and for researchers to ensure that they make participants fully aware about the nature of the data sharing agreements they are entering (using genuinely accessible information documents). These insights have relevance and applicability to not only autism research, but also any scholarship involving marginalised populations making decisions about open data.