Adenomyomatosis of the gallbladder is considered an acquired pathologic condition that affects adults, with only 2 cases previously described in childhood. We report on a 5-year-old boy with incidental detection of this lesion by ultrasonography. Pathologic and clinical assessments are discussed in addition to treatment decision-making, including current insights into the relation between adenomyomatosis and malignancy of the gallbladder. The liberal use of ultrasonography in children with abdominal pain may result in detection of an increasing number of asymptomatic patients. Caregivers should be aware of this condition and its therapeutic implications in the pediatric population.