The genus Berthellina Gardiner 1936 (Mollusca: Heterobranchia: Nudipleura) is a circumtropical group of pleurobranchid sea slugs including species with uniform coloration patterns, varying from yellow and orange to red. The systematics of Berthellina is in need of a revision for many areas of the world, particularly in the Indo-West Pacific region, where more than one species seem to occur. In this paper, we examined specimens of three color morphs collected from the Egyptian coast of the Red Sea. Based on sequence data from two mitochondrial genes, cytochrome c oxidase I (COI) and 16S ribosomal RNA (16S), as well as the nuclear histone 3 (H3) gene, and using phylogenetic and species delimitation approaches, we determined that two species of Berthellina co-occur in the Egyptian coast of the Red Sea. Molecular phylogenies and a revision of the literature confirmed that B. citrina is the correct name for the orange and yellow color morphs, whereas the red color morph is most likely B. delicata. Morphological and anatomical data corroborated the molecular results. This paper constitutes the first record of B. delicata from the Red Sea. Further molecular phylogenetic studies are necessary to provide a comprehensive phylogeny for Berthellina and resolve outstanding questions on the identification and distribution of most species.