Increased caregiving demands from raising an autistic child result in reduced social support, increased parenting stress, and decreased relationship satisfaction for their parents. While social support is protective against parental stress and can increase relationship satisfaction, few studies have examined the relationships between the support networks, functions of support (e.g., informational, emotional, and instrumental), and well-being of parents of autistic children. This study surveyed 112 parents (73 mothers and 39 fathers) of autistic children (aged 5–12 years) online to examine the relationships between (1) who was identified as a primary support person (PSP), (2) which functions of support parents perceived from their PSP, (3) how stressed parents reported they were, and (4) how satisfied parents were with their relationship with their PSP. Results indicated parents most frequently identified a friend or family member as their PSP, emotional support was the most frequently identified function of support, and emotional support had the strongest association with relationship satisfaction. The results of this study provide a foundation for future studies on the implications of support networks, functions of perceived support, and stress on the relationship satisfaction of parents of autistic children.