Abstract Background Raising a child with an autism spectrum disorder (ASD) is a severe stressor and parents often present high levels of depression. Depression is associated with illness perceptions but this association has not been studied in parents of ASD offspring. Objective We aimed to assess the prevalence of psychological distress symptoms and their associations with illness perceptions in parents with an ASD offspring. Methods In 111 parents of ASD offspring we assessed depressive symptoms (PHQ-9), illness perceptions (B-IPQ) and general psychological distress (GHQ-28). Multiple linear and logistic regressions were used to assess their independent associations. Results The prevalence of parental clinically significant depressive symptoms was 34.2%, while 55% presented clinically significant levels of general psychological distress. Younger parents and those with lower financial resources had greater psychological distress and more severe depressive symptoms. Parents felt that the condition impacted their lives and believed it would be chronic. Their beliefs about the consequences and the chronicity of the disorder were significant independent correlates of their psychological distress and depressive symptoms severity. Conclusions These findings indicate that a remarkable proportion of parents with an ASD offspring present clinically significant depressive symptoms, which were associated with illness perceptions relevant to the consequences and the chronicity of the disorder. Our data encourage psychotherapeutic interventions aiming to support parents to deal with the consequences and chronicity of their offspring's disorder, in order to reduce parental psychological distress.