Letrozole is one of the hormonal anticancer drugs which can be employed to treat aromatase dependent breast cancer. Aromatase is an enzyme that catalyses biosynthesis of estrogen from testestrone (androgen).Letrozole was loaded onto pegylated niosomes through reverse phase evaporation technique. Letrozole pegylated niosomes was characterized by dynamic light scattering spectroscopy (195.2 nm pegylated niosome and 234.1 nm letrozole pegylated niosomes), scanning electron microscopy and its entrapment efficiency was calculated to be 66.6% . The drug released pattern (in vitro) from the pegylated niosomes was studied through zero order, first order, Higuchi and Hixson – Crowell kinetics models. It was found that the release pattern followed first order and Hixson- Crowell models. Finally, the IC50 values for pure letrozole and letrozole pegylated niosomes were found to be 0.051 μM and 0.0287 μM, this indicated that the toxicity of drug pegylated niosomes is more than the pure drug.