Phenolic compounds are widely distributed in nature and, according to this paper, pistachio hull is a natural source of phenolic compounds. Water extracts were found to have high phenolic contents (32.0–34.0 mg/gdw of sample), so the best method for extraction of phenolic compounds was solvent extraction with water or methanol. These results suggest that the PHEs possess antioxidant properties and could be used as alternative natural antioxidants (but after toxicological examination). No single compound can be considered responsible for this stability. This study will provide bases for future studies in this area. It is recommended that other common pistachio varieties be examined for antioxidant properties.