Purpose: Family carers of patients with amyotrophic lateral sclerosis (ALS) are presumed to have frequent involvement in decision-making for symptom management and quality of life. To better understand and improve decision-making, we investigated the range and extent of carer participation in decision-making. By focusing on the perspectives of ALS support carers, the study aimed to explore carer participation in decision-making, to identify carer roles, and determine the facilitators and barriers to carer participation in decision-making for ALS multidisciplinary care. Participants and methods: An exploratory, in-depth study was conducted with eight carers of ALS patients from two specialized ALS multidisciplinary clinics. Carers participated in semi-structured interviews that were audio recorded and transcribed then coded and analyzed for emergent themes. Results: Carers made a significant contribution to ALS decision-making. Their roles were: promoting the patient voice, promoting patient health literacy, and providing emotional support and logistical assistance. Facilitators of carer participation in decision-making were perceived to be: health professional endorsement of patients' decision-making style; access to credible information sources; evidence-based information from the ALS clinic, ALS support association, and health practitioners; supportive relationships with family and friends; spiritual faith; ease of contact with ALS services; and availability of physical and practical support for carers. Barriers to carer participation included: changes to patient communication and cognition; conflict between respect for patients' independence and patients' best interest; communication breakdown between patient, carer, and service providers; the confronting nature of disease information; credibility of Internet sites; carer coping strategies; lack of support for the carer; and the burden of care. Conclusion: Carers enhance ALS patient-centered care through their participation in decision-making. They collaborate with patients and health professionals to form a decision-making triad within specialized multidisciplinary ALS clinical care. Nevertheless, health professional engagement with carers as collaborative partners is acknowledged to be a significant challenge.