In the course of screening for reactive oxygen species scavengers from natural products, two antioxidants were isolated from the edible mushroom Polyozellus multiflex and identified as polyozellin and thelephoric acid. Thelephoric acid inhibited 45.7% of the super oxide anion radical, 74.6% of the hydroxyl radical, and 44.0% of the DPPH radical at 0.1 mM, while the positive control ${alpha}-tocopherol$ did 22.1%, 75.6%, and 26.5% of each radical, respectively. Polyozellin, the reductive acetylated form of thelephoric acid, showed almost same scavenging activity against above mentioned radicals. The isolated compounds showed scavenging activity on the superoxide anion radical in the ESR method ($IC_{50}$ of polyozellin and thelephoric acid were $218.0;{mu}M$ and $21.1;{mu}M$, respenctively). However, they showed no significant activity on the hydrogen peroxide radical.