In the present study, 96 co-residing mothers of adolescents and adults with an autism spectrum disorder (ASD) participated in an 8-day diary study and reported on their daily experiences. In comparison with a nationally representative sample of mothers of children without disabilities, mothers of adolescent and adult children with ASD spent significantly more time providing childcare and doing chores, and less time in leisure activities. Fatigue, arguments, avoided arguments, and stressful events were also more common among mothers of individuals with ASD. However, mothers of individuals with ASD reported similar levels of positive interactions and volunteerism as the comparison group. Daily experiences were subsequently related to well-being in both groups. These findings highlight the need for family support services.