Caregivers of children with autism spectrum disorder (ASD) self-report more prospective memory (PM) failures compared with controls. Subjective and objective measures of PM however tend to be poorly correlated. This study therefore explored the cognitive impact of caring for a child with ASD using the Cambridge Prospective Memory Test (CAMPROMPT), a more objective, performance based, assessment of PM failures. Whether atypical cortisol secretion patterns might mediate caregivers’ compromised cognition was also explored. A sample of n=23 caregivers of children with ASD and n=11 parent controls completed time and event cued PM tasks with CAMPROMPT. Diurnal cortisol indices, the cortisol awakening response, diurnal cortisol slope and mean diurnal output were estimated from saliva samples on multiple days. Results indicated objectively assessed event, but not time, cued PM failures were greater in caregivers compared with controls. Variations in cortisol secretion patterns however did not mediate the group effect. In conclusion, caring for a child with ASD was associated with greater deficits in event cued PM. Future studies might examine the influence of caregivers’ event cued PM failures on quality of provided care.