The milk thistle plant is one of the famous plants that have been gaining popularity for its therapeutic potential for centuries. Milk thistle seed oil (MTSO) has been subjected to extensive research. The fixed oil was extracted from the seeds of Silybum marianum (L.) using petroleum ether as a solvent by a soxhlet device. GC-MS was used to identify the chemical composition of the oil. The antioxidant activity of MTSO was tested by the ABTS method, which showed the ability to inhibit lipid peroxidation. In addition, antimicrobial and antifungal investigations were examined. It proved that MTSO has an inhibitory effect against Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli), and antifungal effects (Candida albicans). MTSO has a slightly higher effectiveness against fungi than bacteria.Moreover, the cytotoxic activities of the oil on hepatocellular and colorectal carcinoma were examined. MTSO has shown a moderate cytotoxic effect on the HCT-116 cell line and a weak effect on HePG-2. Whereas; in vivo study has been done on five diagnosed patients who have impaired liver function, and were recruited for the study. Their weight ranged from 100 ± 30 kg, their age range was between 39 -50 years. Each patient was given ten drops of MTSO daily and added to a little water for a four-week study period. MTSO has effects to improve the function of the injured liver. The present work aims to study Milk thistle seed oil, for estimating its pharmacological properties for the liver. This study focused on showing the importance of milk thistle seed oil in our lives as a source of antioxidants, anti-bacterial and anti-fungal, and as an anti-cancer of the liver and colon. It also sheds light on its importance as a treatment for impaired liver, function and fatty liver, due to its improvement in all liver function markers, so it can be hired as an effective human therapy.