Three new coumarins, phellodenols F—H (1—3) and a new glutaric acid derivative, phellodendric acid-A (4) were isolated from the leaves of Phellodendron amurense together with twenty-nine known compounds. Extensive 1D and 2D NMR experiments and other spectroscopic studies were employed to determine the structures of 1—4. The isolated compounds were screened for their antioxidant activity through DPPH (α,α-diphenyl-β-picrylhydrazyl) radical scavenging assay. Compounds quercetin, quercetin-3-O-β-D-glucoside, quercetin-3-O-β-D-galactoside and kaempferol-3-O-β-D-glucoside demonstrated significant radical scavenging activity comparable to vitamin E.