BACKGROUND AND OBJECTIVES: Little is known about the 2% of US children being raised by their grandparents. We sought to characterize and compare grandparent-and parent-headed households with respect to adverse childhood experiences (ACEs), child temperament, attention-deficit/hyperactivity disorder (ADHD), and caregiver aggravation and coping. METHODS: Using a combined data set of children ages 3 to 17 from the 2016, 2017, and 2018 National Survey of Children's Health, we applied survey regression procedures, adjusted for sociodemographic confounders, to compare grandparent-and parent-headed households on composite and single-item outcome measures of ACEs; ADHD; preschool inattention and restlessness; child temperament; and caregiver aggravation, coping, support, and interactions with children. RESULTS: Among 80 646 households (2407 grandparent-headed, 78 239 parent-headed), children in grandparent-headed households experienced more ACEs (b = 1.22, 95% confidence interval [CI]: 1.07 to 1.38). Preschool-aged and school-aged children in grandparent-headed households were more likely to have ADHD (adjusted odds ratio = 4.29, 95% CI: 2.22 to 8.28; adjusted odds ratio = 1.72, 95% CI: 1.34 to 2.20). School-aged children in these households had poorer temperament (b adj = .25, 95% CI: 20.63 to 1.14), and their caregivers experienced greater aggravation (b adj = .29, 95% CI: 0.08 to 0.49). However, these differences were not detected after excluding children with ADHD from the sample. No differences were noted between grandparent-and parent-headed households for caregiver coping, emotional support, or interactions with children. CONCLUSIONS: Despite caring for children with greater developmental problems and poorer temperaments, grandparent caregivers seem to cope with parenting about as well as parents. WHAT'S KNOWN ON THIS SUBJECT: Nearly 3 million children today are raised by their grandparents, often because of social adversity. Research to date has primarily demonstrated negative social and health outcomes for caregivers and children in grandparentheaded households. WHAT THIS STUDY ADDS: In a large, nationally representative US sample, attention-deficit/hyperactivity disorder and childhood adversity appear to be responsible for some of the behavioral and developmental disparities observed between grandparent-and parent-headed households. No differences in caregiver coping and emotional support were found.