Domitius lusitanicus (Fage, 1931) is a troglobiont spider, endemic from caves in the largest karst massif in Portugal, the Estremenho. It was the first described cave-adapted species from Portugal, but the male of the species was only described in 1988. Over the last two decades, the knowledge on the distribution of D. lusitanicus increased significantly. We assess the conservation status of D. lusitanicus , providing new information on its extent of occurrence and the anthropogenic threats, and present a IUCN Red List profile. D. lusitanicus faces various anthropogenic threats, such as habitat loss, agriculture, pollution, and tourism impacts. Despite a large part of its distribution is included in a Natural Park, it expands outside of the areas deemed for protection in the Natura 2000 network. This species has the widest spread distribution of all troglobionts in the Estremenho Massif, therefore it may be used as an umbrella species for the protection of other cave-adapted species of the massif.