Raising a child with an Autism Spectrum Disorder (ASD) presents significant challenges for parents that potentially have a impact on their health and wellbeing. The current study examined the extent to which parents experience fatigue and its relationship to other aspects of wellbeing and parenting. Fifty mothers of children with an ASD aged 2-5 years participated in the study. Compared with mothers of typically developing children, mothers of children with an ASD reported significantly higher fatigue, with overall scores in the moderate range. Factors associated with high levels of fatigue were poor maternal sleep quality, a high need for social support and poor quality of physical activity. Fatigue was also significantly related to other aspects of wellbeing, including stress, anxiety and depression, and lower parenting efficacy and satisfaction. The need for interventions to specifically target parental fatigue and its impact on families affected by ASDs both in the short and long term is clearly indicated.