Mesenchymal hamartoma of the liver is a rare, benign tumor that presents mostly before the age of 2 years. Its pathogenesis is poorly understood. We present the case of a 2.5-year-old female patient who had a large cystic mass of the liver of which the hamartomatous nature was confirmed by the pathological examination of the surgical specimen. We discuss the clinicopathological, imaging, and histological features of this unusual tumor through a review of the literature.