Human carboxylesterase 1 (HCE1), belonging to a multigene serine hydrolase family, is a major liver carboxylesterase responsible for the hydrolysis and metabolism of various xenobiotics. It also plays an important role in the transportation and metabolism of endogenous cholesterol ester and free fatty acid, and is closely associated with the pathogenesis of hepatocellular carcinoma. This review describes current developments in the molecular structure, the roles in drug, toxins and lipid metabolism, and the early diagnosis for hepatocellular carcinoma of human carboxylesterase 1.