Background The Montseny brook newt (Calotriton arnoldi) is an endemic amphibian present only in the Montseny area and classified as “critically endangered” in the IUCN Red List. The population of this amphibian is estimated to be fewer than 1 500 adults. Moreover, its distribution area is small and fragmented, covering less than 8 km2. The newt species is adapted to mountain streams and requires a pristine habitat. It is adversely affected by climate change and human activities. Although some populations disappeared in the 20th Century, probably due to the lack of a stable water flow, most are seemingly stable nowadays. Nevertheless, some populations have an “unfavourable” conservation status, mainly caused by melanocytosis (pigmented skin tumours), which could indicate adverse micro-environmental changes. Objectives The main objective of the Life Tritó Montseny project is to improve the conservation status of the Montseny brook newt and its riparian habitat. Specific objectives are to: Ensure the conservation of the genetic pool of the species and to expand its geographic distribution area; Increase the hydrological quality and water flow quantity of streams in its range of distribution; Eliminate or minimise current threats in the riparian habitat where the species is found; Establish suitable legal protection at national and European level and to develop a management plan for the species; Monitor regularly its conservation status and increase scientific and technical knowledge on its conservation and management; and Involve and engage stakeholders in the conservation of riparian habitats, their biodiversity and, specifically, the Montseny brook newt. Expected results: Consolidation of the breeding centres: 90% of the genetic variability of natural populations, no body anomalies and quadruple larvae production. Doubling the number of streams with Montseny brook newt by reintroduction of individuals, creating six new populations; Captive breeding centres to quadruple larvae production and produce newts with 90% of the genetic variability of natural populations and no body anomalies; Consolidation of existing wild populations; Reduction in water extraction from streams with Montseny brook newt (90% of surface water catchment systems to be improved or eliminated); Improvement of wastewater treatment in 75% of houses in the range of the Montseny brook newt; Installation of collection and reuse of rainwater and grey water in 50% of the houses in the newt’s range; A 90% increase in river connectivity at intersections between roads, tracks and streams holding the Montseny brook newt; A 50% increase in the area of native riparian forest and increased biological quality; Drafting and approval of a conservation plan and action programme for the Montseny brook newt; Legal recognition of the species at national and European level; Annual monitoring of the conservation status of the Montseny brook newt, using improved monitoring stations; Greater knowledge of the biology and ecological requirements of the species; Transfer of all data gathered by the project to the PN-RB Montseny information system and to the Global Biodiversity Information Facility (GBIF); and A comprehensive communication and dissemination strategy (website, scientific articles, events, good practice guidelines, school visits, etc.).