Objective The aim of the present study was to explore the use of complementary consent methodologies to support a potentially vulnerable group of people, namely those aging with intellectual disability, to provide personal input. It was premised on the view that processes to determine capacity for consent, appropriately modified to account for individual capabilities and current circumstances, could facilitate meaningful participation in the development of personal health care plans of people previously excluded from contributing.Methods The present descriptive case study research was undertaken in New South Wales, Australia. A seven-step process for determining capacity for consent was developed, and 10 participants aged between 54 and 73 years with lifelong intellectual disability and health comorbidities were involved. A variety of assistive communication tools was used to support individuals to demonstrate their capacity for giving informed consent.Results After being provided with tailored support mechanisms, seven participants were considered to meet all seven components for determining capacity for consent. Three participants were deemed not to have capacity to give consent regardless of the type of support provided.Conclusions Three critical factors for facilitating personal involvement in decision making for individuals with an intellectual disability were identified: (1) defining consent specifically for the target outcome; (2) outlining the criteria needed for consent to be obtained; and (3) using appropriately modified alternative communication mechanisms as necessary.What is known about the topic? Self-determination is one of the fundamental principles of human rights legislation around the world and, as such, it is considered desirable to have personal input by individuals into the development of their own health care plans. However, this is not always considered feasible if the person comes from a group in the community perceived to be vulnerable to exploitation and viewed as lacking capacity to give informed consent. This results in the use of proxy respondents, who may not accurately represent the desires and life aspirations of the individual.What does this paper add? This paper examines the development and implementation of a targeted program to support individuals aging with lifelong intellectual disability to demonstrate their capacity to provide informed consent. Specifically, it outlines how alternative communications methods, tailored to personal needs and capacity, can assist an individual to both understand and then confirm their understanding of consent in order to participate in developing health care plans.What are the implications for practitioners? People with intellectual disability are now living longer and are increasingly at risk of serious health conditions. The development of long-term health management plans has traditionally not included individuals with more complex needs and moderate intellectual disability, but the present study shows that members of this cohort can successfully understand and consent to participate in health care decision making. By proactively supporting this process, community and healthcare settings may be able to directly facilitate contribution from more individuals, therefore better meeting the goal of person-centred support.