Until now, an exhaustive list of Panamanian heterobranch sea slugs (Mollusca: Gastropoda) had not been made. Here, we present a descriptive list of all species of sea slugs off of the coasts of Panamá, based on published references and confirmed photographs of collected species. All publications referring to collections of these gastropods were compiled and examined, and specimens were collected from different coastal areas of Panamá. The resulting catalog contains 232 species of heterobranch sea slugs, of which 117 are found on the Caribbean coast and 127 are found on the Pacific coast. Eight species have a bicoastal distribution, and 18 species have an amphi-Atlantic distribution. This study confirms the high biodiversity of heterobranch sea slugs inhabiting the Panamanian coasts. However, because the Pacific coast has been less well studied, future research should include more extensive sampling in these locations.