Purpose <p>Parenting a child diagnosed with Autism Spectrum Disorder (ASD) often entails ongoing emotional challenges that can contribute to parental burnout. This study aimed to investigate the mediating and moderating roles of emotional reactivity in the relationship between psychological flexibility and parental burnout among parents of children diagnosed with ASD.</p> Methods <p>A total of 230 parents (74.8% female; M<i>age</i> = 40.14, <i>SD</i> = 8.27) participated in the study. Participants were recruited through convenience sampling from special educational centers. Mediation and moderation analyses were conducted using the PROCESS macro for SPSS to test indirect and conditional effects of emotional reactivity.</p> Results <p>Emotional reactivity partially mediated the association between psychological inflexibility and parental burnout. Higher psychological inflexibility was linked to greater emotional reactivity, which in turn predicted higher parental burnout. Moreover, emotional reactivity significantly moderated this relationship (ΔR² = 0.009, <i>p</i> = .025), indicating that the association between psychological inflexibility and parental burnout was stronger among parents with higher emotional reactivity.</p> Conclusion <p>These findings suggest that interventions aimed at reducing psychological inflexibility and managing emotional reactivity may help mitigate parental burnout among parents of children with ASD.</p>