Zanthoxylum nitidum is commercially used in healthcare products for the improvement of tooth condition. Its fruit is also used as a spice. Three new benzenoids, (E)-4-(4-hydroxy-3-methylbut-2-enyloxy)benzaldehyde (1), (E)-methyl 3-(4-((E)-4-hydroxy-3-methylbut-2-enyloxy)phenyl)acrylate (2), and (Z)-methyl 3-(4-((E)-4-hydroxy-3-methylbut-2-enyloxy)phenyl)acrylate (3), have been isolated from the stem wood of Z. nitidum, together with 17 known compounds (4–20). The structures of these new compounds were determined through spectroscopic and MS analyses. Compounds 8–10, 13, 14, 17, and 18 exhibited inhibition (IC50 ≤ 7.95 lg/ml) of superoxide anion generation by human neutrophils in response to formyl-L-methionyl-L-leucyl-L-phenylalanine/cytochalasin B (fMLP/CB). Compounds 7–9, 13, 14, and 17 inhibited fMLP/CB-induced elastase release with IC50 values ≤7.45 lg/ml.