Recent examinations of some marine fishes from off the coast of South Australia revealed the presence of two species of Philometra Costa, 1845 (Nematoda: Philometridae): P. inconveniens n. sp. from the ovary (males) and body cavity (subgravid female) of the southern garfish Hyporhamphus melanochir (Valenciennes) (Beloniformes, Hemiramphidae) and Philometra sp. (gravid and subgravid females) from the body cavity of the Australian barracuda Sphyraena novaehollandiae Günther (Perciformes, Sphyraenidae) (new host and geographical records). Specimens of species are described and illustrated based on light and scanning electron microscopical examinations. Philometra inconveniens n. sp. differs from the most similar species P. longa Moravec, Barton & Shamsi, 2021, a parasite of the body cavity of the congeneric host off eastern Australia, mainly by a different structure of the gubernaculum (absence of dorsal barbs and presence of lateral extensions on its distal portion). This indicates a high degree of host specificity of these nematodes in co-occuring congeneric hosts.