A new woodlouse species of the genus Buchnerillo Verhoeff, 1942 is described and illustrated from the Cantabrian Coast of Asturias (Eastern Atlantic Ocean of the Iberian Peninsula). Buchnerillo atlanticus sp. nov. is a halophilic woodlouse that lives under embedded rocks in fine-grained sand areas of its type locality beach. Its morphological features, including secondary sexual characteristics, allow it to be distinguished from the other three known species of the genus Buchnerillo. Biological, ecological and ethological data of the new species are commented. To facilitate the separation of the four known species of Buchnerillo, the main diagnostic features are summarized and their known distribution is commented.