A new species of the genus Phyllodiaptomus Kiefer, 1936, is herein described as Phyllodiaptomus irakiensis sp. nov. from the Shatt al-Arab River, southern Iraq. The species is closely similar to Phyllodiaptomus blanci (Guerne & Richard, 1889), but can be distinguished from that species by the left metasomal wing in the female, the second and third urosomal somites each having a conspicuous hyaline lobe on the dorsal side, the presence of fine hairs at the outer and inner margins of the furcal rami, and the structure of the fifth pair of legs in both sexes; moreover, the anal segment along with the furcal rami in the male are curved to the right inner side of the main axis of the urosome, in addition to differences noticed in the right antennule, etc. The new species is the eleventh member of the genus (cf. Sanoamuang & Teeramaethee, 2006) and the second species recorded from southern Iraq.