Many lichen secondary metabolites contributed to the field of pharmacology as an active ingredient of different drugs for years. In the present study, we aimed to test the anticancer activity of olivetoric acid (OA), which we isolated from Pseudevernia furfuracea (L.) Zopf in human hepatocellular carcinoma cells (HepG2). In addition, we used non-tumoral human liver cells (THLE2) to test the level of side effects of OA in vitro. For this purpose, cytotoxic (apoptotic and necrotic), oxidant, genotoxic activities and expression levels of apoptotic genes caused by different concentrations (12.5-400 mg/L) of OA were tested on both cells. Flow cytometric and cytotoxicity tests (MTT and LDH) revealed that OA (100-400 mg/L) had a higher rate of apoptotic effects on HepG2 cells compared to THLE2. Total oxidative stress and oxidative DNA damage levels caused by all concentrations of OA on HepG2 cells was significantly (p < 0.05) higher compared to negative control. Trials with concentrations of 100-400 mg/L significantly (p < 0.05) increased total antioxidant capacity on THLE2 cells compared to the control group. As a result, based on human hepatocellular carcinoma, it is hoped that OA may contribute to the combined or alternative treatment process.