While the impact of raising a child with an Autism Spectrum Disorder (ASD) is well documented, with mothers reporting higher levels of stress than mothers of children with other disabilities, positive maternal outcomes have also been identified. What remains unclear, however, is the role of child age on maternal outcomes. We sought to clarify the role of child age in maternal stress and family quality of life (FQoL) in mothers raising a child with ASD. Participants included 140 mothers of children aged 3-16 years grouped to represent four key stages of childhood (preschool, early school years, middle school, early high school). Using a cross-sectional design, mothers completed questionnaires assessing potential risk (e.g., child problem behaviour, symptom severity) and protective (e.g., family characteristics) factors attributed to maternal outcomes. The results revealed significant age related group differences in child internalising behaviour and ASD symptomatology between the early and middle school years. Lower levels of adaptive social behaviour in older age groups were also found. Although mothers of older children reported significantly less support from professionals than mothers of younger children, no significant age effects were found to contribute to maternal reports of stress or FQoL. The current findings support the view that mothers appear to demonstrate stable levels of stress and FQoL despite fluctuations in key child variables and a reduction in supports, across age, highlighting the ongoing nature of maternal needs and heightened levels of child symptomatology during adolescence.