Aim <p>Families of children with autism spectrum disorder (ASD) face considerable mental health problems. Social support has been identified as a crucial buffer against these stressors, with socioeconomic factors significantly impacting how people perceive their social support. Thus, we hypothesized that social support would mediate the relationship between family income and mental health issues in mothers of children with ASD.</p> Subject and methods <p>This study used data from the SOLACE-Brasil project, a web-based cross-sectional survey conducted during the COVID-19 pandemic. The survey targeted mothers of children with ASD, achieving a final sample of 1924 mothers. Mental health was assessed using the Depression, Anxiety, and Stress Scales (DASS-21), and perceived social support was measured using the Multidimensional Scale of Perceived Social Support (MSPSS). Statistical analyses, including path analysis, were conducted to explore the complex relationships between family income, social support, and mental health.</p> Results <p>High levels of co-occurring anxiety and depression (35.8%) were observed among mothers of children with ASD. Low income was associated with a higher prevalence of mental health disturbances and with lower perceived social support. Path analysis revealed that family income can directly impact mental health issues, but also that social support mediated the relationship between family income and co-occurring anxiety and depression.</p> Conclusion <p>These results highlight the critical role of social support in mediating the impact of financial strain on the mental health of mothers of children with ASD. Interventions aimed at decreasing financial strain and improving social support networks could alleviate the mental health burden in this population.</p>