A solitary liver cyst (SLC) is a nonparasitic cyst of congenital origin. Its cause is unknown, but it may develop in the form of a simple cyst or a biliary cyst. Solitary liver cysts are extremely rare and usually symptomatic in infancy whereas they are most often detected incidentally in adulthood. Despite advanced imaging techniques, the differential diagnosis of SLC may still be difficult. Surgical intervention is required for histopathological verification, to relieve symptoms and prevent complications such as infection, cyst rupture, and hemorrhage. Although total excision of SLC is desirable to impede recurrences, partial excision may be adequate when total excision is impossible. We report the case of a newborn with a progressively enlarging solitary intrahepatic biliary cyst. We discuss the etiology, differential diagnosis, and treatment options for this rare entity.