Introduction: Cassia is scientifically known as Cinnamomum Cassia, and it is a member of the Lauraceae family. Cassia is the botanical name for the Cassia bark. Cassia cinnamon is also used for chest pain, high blood pressure, kidney disorders, cramps, and cancer. Aim: The present study was designed to analyse the anticancer activity of cassia oleoresin mediated selenium nanoparticles in HepG2 liver cancer cell line. Materials And Method: Cassia oleoresin was obtained from synthite industries Ltd,Kerala. MTT assay was performed using HEPG2 cell lines to asses the anticancer activity.The HEPG2 cell were treated with different concentration of cassia oleoresin mediated selenium nanoparticle (20,40,60,80,100,200μg/ml) for 24 hours and the cell viability was analysed . Results: The results of MTT assay showed a dose dependent decrease in cell viability of cassia oleoresin mediated selenium nanoparticle against the HEPG2 liver cancer cell line.In the HepG2 cell line, the oleoresin induced selenium increased cytotoxicity in a dose-dependent manner. The maximum cytotoxic effect was observed at a dose of 200μg/ml, which was used in the study.The IC50 value was 15μg/ml. Conclusion: The present study within the limitations conclude that cassia oleoresin mediated selenium nanoparticles possess a good level of cytotoxic activity against HEPG2 cell lines. Hence the extract may be further explored in animal models to establish its activity