Ionic Liquids (ILs) are salts with low melting point, which are typically composed of organic or inorganic anions and an organic cation associate to one or more alkyl chain substituent. These compounds can increase the activity/stability of enzymes. In this sense, this work evaluated the effects of imidazolium chloride based ILs on the activity of lipase from Aspergillus niger. It was studied the following ILs: [C8mim]Cl, [C10mim]Cl and [C12mim]Cl in different concentrations through 24 hours. ILs with shorter alkyl chain increased the lipase activity and kept it until 24 hours independent of IL concentration used. In this way, the alkyl chain of imidazolium ILs presents high influence in the activity/ stability of lipase.