During a recent cruise to investigate the cold-water coral habitats in the eastern Gulf of Mexico seven scale worm species (Polychaeta: Aphroditiformia) were found, with four of them new to science: Laetmonice tunicata sp. nov. (Aphroditidae); Eunoe purpurea Treadwell, 1936, Gorgoniapolynoe caeciliae (Fauvel, 1913), Harmothoe dannyi sp. nov., Harmothoe cedrici sp. nov. and Subadyte campechensis sp. nov. (Polynoidae); and Leanira robusta Verrill, 1885 (Sigalionidae). An extended taxonomic account is given for all species, with detailed descriptions and figures for the new species. Three of the five polynoid species were found associated with a coral host: E. purpurea with Bathypathes cf. alternata Brook, 1898 (Antipatharia); G. caeciliae with Acanthogorgia armata Verrill, 1878 and Candidella imbricata (Johnson, 1862) (Octocorallia) and H. dannyi sp. nov. with Stylaster erubescens Pourtalès, 1868 (Hydrozoa). These associations are characterized in detail and documented by in situ ROV pictures and microscopic images and videos of the live animals, together with their respective host.