Ramaria botrytis is a popular mushroom in Asian countries, particularly known for its crispy texture and rich nutrient content. In this study, we found potent lipid peroxidation-inhibiting activity in this mushroom and identified the active compound associated with this activity as pistillarin. To our knowledge, this is the first report of the presence of pistillarin in R. botrytis. Our study is the first to investigate the inhibitory effects of pistillarin against physiological reactive oxygen species such as 1O2, •OH, and O2- and lipid peroxidation, which damages living tissues. We also clarified its characteristic antioxidant activities, with no 1O2 and •OH quenching activity (IC50 > 100 μМ), moderate O2- quenching activity (IC50 of 10.2 μМ), and potent lipid peroxidation-inhibiting activity (IC50 of 0.66 μМ), for the first time. Furthermore, we found a new pistillarin-related compound (pistillarin B) in salted R. botrytis. We isolated pistillarin B, determined its structure, and examined its lipid peroxidation-inhibiting activity (IC50 of 6.88 μМ).