Coordinated research efforts in mesophotic coral reefs are only a decade old, but have already produced exciting findings in ecology, physiology, geomorphology, population genetics, biodiversity, and taxonomy. In this taxonomic contribution, we describe both sexes of a new copepod species of the family Novocriniidae Huys and Iliffe in Zool Scr 27(1):1–15, 1998 from a mesophotic coral reef off southwestern Puerto Rico. This is only the fifth species of the family and the fourth of the genus Atergopedia Martínez Arbizu and Moura in Zool Beitr NF 38:189–210, 1998. The new species, Atergopedia dowgialli sp. nov., shares the following characters with its three congeners: 1) antenna without seta on the first endopodal segment; 2) lateral armature of the female antenna shows a multiplication of distinct setae and consists of one geniculate seta followed by five or more slender setae; 3) the first endopod segment of the first swimming leg P1 bears no inner seta; 4) male fifth leg with two spines on endopodal lobe; and 5) the exopod of the fifth swimming leg fused to basendopod in the female. Atergopedia dowgialli sp. nov. is characterized by the loss of the basal seta in both antenna and maxilliped, the loss of the first maxilla endite, the presence of a long process between the outer and distal elements of the leg 1 exopodite 3, which is stronger and longer in the female, and the possession of a very short and strongly ornamented furca in both sexes. The genus Atergopedia has been found in deep and relatively shallow habitats from the Arctic Ocean to the Caribbean. In contrast, almost all species of the taxon Novocrinidimorpha, which includes the families Novocriniidae, Superornatiremidae Huys 1996, and Rotundiclipeidae Huys 1988, have been found associated with anchialine caves, indicating a derived distribution for Atergopedia.