Sleep disturbance is prevalent in caregivers and associated with negative physical, mental, and functional outcomes. This study examined the effects of sleep disturbance on daytime functions (sleepiness, fatigue, mood, cognitive alertness), care-related quality of life, and daily parenting interactions in 20 mothers of children with autism spectrum disorder for 10 consecutive days using ecological momentary assessment design. Participants responded about daytime functions four times and care-related quality of life and daily parenting interactions once using an online survey. Sleep disturbance was significantly related to all daytime functions and frustration with childcare. Therefore, development of sleep hygiene interventions is warranted to effectively reduce the impact of sleep disturbance and enable these mothers to better tackle daily physical and mental challenges.