Milk thistle (Silybum marianum) has been widely recognized for its bioactive properties, owing to its rich content of phytochemicals. This study presents a comprehensive analysis of milk thistle extract, focusing on its antioxidant and antimicrobial properties, as well as its phytochemical composition. Using Gas Chromatography-Mass Spectrometry, we identified a diverse array of phytochemicals in milk thistle extract. These included fatty acids (oleic acid, linoleic acid, cis-vaccenic acid), flavonoids (silybin A, silybin B and isosilybin A), and other phenolic compounds (phytol acetate and iso flavone derivative). The antioxidant activity of the milk thistle extract was substantial, with a total antioxidant activity of 21400 mg ascorbic acid equivalent/ kg. The total phenolic content was 10898.75 mg Gallic acid equivalent/kg, and the total flavonoid content was 4116 mg quercetin equivalent /kg. The extract also exhibited high free radical scavenging, ferric-reducing power, and hydrogen peroxide inhibition activities. The pigments contents of the extract were 0.039 and 1.45 mg/g for chlorophyll and carotenoids, respectively. Antimicrobial tests revealed the extract's ability to inhibit several Gram-positive and Gram-negative bacteria, such as Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus, as well as fungi like Candida albicans and Aspergillus species.  These findings underscore the potential of milk thistle extract as a natural antioxidant and antimicrobial agent. Given the rising concerns over chemical additives, the milk thistle extract could offer a promising alternative to food and feed additives to promote health and prevent diseases.