BACKGROUND AND OBJECTIVES: Research has yet to seek a more complete understanding of how people aging with intellectual disabilities experience their social relations, and how their earlier life experiences impact the development of their social relations. This study investigated the experiences of older adults with intellectual disabilities with their social relations from a life course perspective. RESEARCH DESIGN AND METHODS: A process of paired recruitment generated a sample of 12 adults with intellectual disabilities age 50 and over with at least one key support person each. Data collection consisted of in-depth qualitative life history interviews with the participants and their key support persons using lifelines. RESULTS: Thematic analysis of the interview transcripts demonstrated that the participants' social relations facilitated positive experiences in the first parts of their lives. The participants felt their lives were disrupted by several transitions as they reached young and middle adulthood such as moving out of the family home, parental divorce and the deaths of parents. Challenging social encounters such as abuse, bullying and conflicts caused distress and negatively impacted the participants' well-being at various points in their lives. Finally, participants simultaneously expressed feelings of belonging and longing as central to their social well-being in late life. DISCUSSION AND IMPLICATIONS: Study findings highlight complex experiences of adults with intellectual disabilities with their social relations across their lives. They promote further development of strategies for person centered planning such as social network mapping and life story work to better support adults with intellectual disabilities as they age.