Newer systemic treatments for advanced hepatocellular carcinoma (HCC) include immune checkpoint blockade (ICB) which act through increasing cytotoxic T-cell mediated response to tumor. There is a lack of biomarkers of ICB response and treatment outcomes are not correlated with change in tumor size. We evaluated MRI imaging features of HCC and change in tumor stiffness after 6 weeks immunotherapy in surgical and non-surgical patients. An increase in HCC stiffness on MRE after 6 weeks treatment was significantly correlated with treatment response. Longitudinal measurement of tumor stiffness on MRE provides a novel technique for early immunotherapy response assessment.