Families of children with autism spectrum disorder (ASD) often experience much more negative perceptions of their family quality of life (FQoL). To investigate key factors that may shape these experiences, we conducted a case–control study of sixty-one Spanish families (29 with a child with ASD) using a broad psychosocial assessment (e.g., ASD severity, social support, demographics), including the first direct test of the relationship between FQoL and parental risk literacy (i.e., the ability to evaluate and understand risk, as measured by numeracy). Results revealed that numeracy was associated with differences in perceived FQoL among families of children with ASD (R2 = .10), a finding that held across several models statistically controlling for the influence of other variables. Findings suggest that parental risk literacy skills may generally be associated with differences in decision making vulnerabilities (e.g., risk evaluation and interpretation) that influence family outcomes including FQoL.