For people with intellectual disabilities, the potential for self-determination depends on both personal characteristics and factors related to the social environment. This study examines barriers and facilitators to self-determination among residents at facilities for people with intellectual disabilities. We held 13 focus group discussions to explore the opinions and experiences of 10 people with mild to moderate intellectual disabilities and 10 social care professionals at three residential facilities in Western Switzerland. We identified environmental, personal, and relational barriers and facilitators to self-determination associated with attitudes, representations, and institutional settings. Within the social environment of people with intellectual disabilities, relationships based on trust, partnership, and collaboration appear to promote self-determined behaviours. Ideally, strategies for promoting self-determination among people with intellectual disabilities should take both personal characteristics and the social environment into account.