Background: Families caring for children with autism spectrum disorder (ASD) have reported poorer family functioning. Social support might strengthen family functioning, but limited research to date has focused on this association in China. Methods: This study conducted a cross-sectional survey of Chinese families that have children with ASD to examine the relationship between social support and family functioning. Caregivers of children with ASD from Sichuan province in China (N = 167) were surveyed concerning their perceived social support and family functioning. The Social Support Rating Scale was used to investigate caregivers’ perceived social support from three dimensions: subjective support, objective support, and the utilization of support. A Chinese version of the Family Adaptability and Cohesion Scale was used to investigate their perceptions of family cohesion and adaptability. The Pearson correlation coefficient and stepwise multiple regression were used for analyses. Results: The results suggested that social support was positively related to family cohesion and adaptability. Of the three sub-domains of social support, both subjective support and the utilization of support were positively associated with family cohesion and adaptability. Conclusion: The study’s findings evidenced the importance of different types of social support and could be used to develop a targeted support service for families that have children with ASD to improve their family functioning and sustain the family unit.