Background: Long-term care planning (LTCP) is critical for individuals with intellectual/developmental disabilities. Objectives of this study were to investigate progression through LTCP, and associations between social support and: (1) LTCP and (2) burden among family caregivers. Methods: A cross-sectional survey was distributed to caregivers of individuals with intellectual/developmental disabilities in NY, OH, PA, and TX, exploring demographics, supports, burden, and LTCP behaviours. Bivariate and linear multiple regression analyses were used to investigate study objectives. Results: Caregivers (n = 405) were predominantly parents, female, non-Hispanic, and in the 'learning to plan' stage of LTCP. Caregiver-identified social support was associated with further progression in LTCP (p = 0.020) and lower caregiver burden (p <0.001). Conclusion: Social support was associated with further progression in LTCP, and associated with less burden, however fewer than 40% of caregivers reported having social support. Ongoing exploration of emotional/social needs of caregivers is necessary to better support these families.