Background Amongst the cave-dwelling millipedes (Diplopoda), there are several endemic species in Portugal with a very small geographical distribution. These species play an important role in the decomposition of organic matter in subterranean ecosystems and are vulnerable to disturbance from human activities, such as habitat destruction, pollution infiltrating from the surface and cave tourism. New information We present the IUCN Red List profiles for cave-adapted millipedes (Diplopoda) from Portugal and propose conservation measures to prevent extinction. Overall, cave-adapted millipedes from Portugal represent an endemic part of the country's biodiversity and conservation efforts will help maintain the delicate ecological balance of subterranean ecosystems.