The new species, Cirrhilabrus briangreenei, is described on the basis of the holotype and six paratypes collected from mesophotic coral ecosystems of the Verde Island Passage, Philippines, between depths of 82 and 110 m. The new species is most closely related to Cirrhilabrus pylei, but it differs primarily in the presence of: more pored scales on the posterior lateral line (7–9 vs. 5–6); a lower number of circumpeduncular scales (14 vs. 16); a lower number of gill rakers (16–17 vs. 18–20); and differences in coloration details of the dorsal and caudal fins. Both species differ from all other congeners in sharing the following combination of characters: pelvic fins very long (56.5–70.0% SL), often extending past anal-fin terminus in males; caudal fin scintillating and iridescent in males; dorsal fin with sinuous scribbling in both sexes; anterior dorsal fin with a metallic blue spot on first one to two interspinous membrane spaces; snout with three parallel stripes from maxilla to anterior edge of orbit; and rest of head with a network of short broken pinstripes in both sexes. These characters are also distributed in part amongst other species of Cirrhilabrus, in particular, C. katoi, C. lineatus, C. rhomboidalis, and C. rubrimarginatus, and their putative relationships are discussed on the basis of meristic, morphometric, and molecular sequence data. We briefly comment on the variability of morphological characters within Cirrhilabrus and their implications towards phylogenetic classification, with remarks on methods for data collection for species of Cirrhilabrus.