Acute cholecystitis in the neonate is rare and usually treated by cholecystectomy. A 1-day-old full-term girl had clinical and sonographic features of acute calculous cholecystitis. This was successfully managed nonoperatively with intravenous fluids and antibiotics, leading to complete resolution of the condition. The infant currently is thriving and asymptomatic with a sonographically normal biliary tree. Spontaneous resolution of cholelithiasis may occur in neonates, even in the presence of acute cholecystitis.