Anilocra montti sp. n. (Isopoda, Cymothoidae) is described from the mouths and branchial chambers of caged salmon and trout from Puerto Montt, Chile. The description is based on a detailed study of 30 male specimens. No females were found, indicating that salminoids are not the normal hosts of the parasite. The new species differs from others in the genus by having carinae on pereopods 4-7, a pleon that is abruptly narrower than the pereon, second pleopods without appendices masculina, a pleotelson that is wider than long and uropods with subequal rami.