Unlike other forms of disaster, terrorism is not confined to a particular place or time, and recent evidence indicates that the 9/11 terrorist attack was a significant macrolevel stressor affecting the health and mental health of United States citizens. No studies, how-ever, have reported symptoms in toddlers and their mothers both before and after the attacks. To address this gap, we examined the effects of the 9/11 terrorist attacks on mothers and their 33-month-old toddlers. The attacks occurred during data collection at 33 months of a longitudinal study. Thirty-three-month-old toddlers and mothers who were assessed after the attacks were compared with those assessed before the attacks. When changes were examined from a previous wave of data collected at 15 months, those in the after-attack group showed poorer health, lower child acceptance, and marginally more anxiety, and their toddlers cried more and slept less, whereas the before-attack group showed no changes. Our findings contribute to research documenting widespread effects of the 9/11 terrorist attack on stress-related symptoms and suggest that greater attention must be placed on the needs of our youngest citizens and their caregivers.