Background: Shared decision-making between patients and primary healthcare professionals positively impacts health outcomes. However, people with intellectual disability face additional barriers and require supported shared decision-making (SSDM) to participate. Little is known about how healthcare professionals use SSDM with this population. This paper explores the facilitators and barriers experienced, and strategies/resources employed by healthcare professionals working with people with intellectual disability. Method: Ten purposively sampled primary healthcare professionals participated in semi-structured interviews. This descriptive qualitative study used content analysis. Findings were compared with a proposed model of factors influencing triadic (the person with intellectual disability, their caregiver and the healthcare professional) SSDM. Results: Five factor categories emerged: previous training/experience; engagement and trust; effective collaboration with caregivers; organisational culture and contexts; and familiarity/confidence with communication support strategies and resources. Conclusions: Healthcare professionals can leverage pre-existing skills and knowledge, but provision of targeted professional development may reduce anxiety and increase successful SSDM.