Molluscs, as a class of invertebrates, are numerous and widespread almost everywhere in the world. As the world is constantly changing, so is the sea as a habitat. Overexploitation and habitat loss are major human drivers of historical changes in biodiversity. Habitat loss and degradation, accompanied by the impact of fishing, pollution, climate change, eutrophication and the presence of invasive species, are considered the most important threats and affect almost all taxonomic groups. Conservation of species diversity is today considered a priority at the global level, and Croatia is also participating in this goal. In our country, the Directorate for Nature Protection of the Ministry of Environmental Protection and Energy of the Republic of Croatia deals with nature and species conservation. Based on the threat assessment, it issues Red Books showing the endangerment of flora and fauna. For the same reasons, numerous associations have been established to deal with the conservation of species and nature. Protected species of molluscs in Croatia are divided into strictly protected native wild species, strictly protected foreign species and protected native wild and foreign species. This Final Paper describes in more detail the current state of the populations of Charonia tritonis, Tonna galea, Episcomitra zonata, Pinna nobilis and Lithophaga lithophaga, which are considered to be the most endangered mollusk species in the Adriatic Sea.