The results of our analysis of the Caulinia minor distribution in the Nizhny Novgorod region on the basis of published sources, herbaria samples and the authors’ original data are presented. The species preferring water bodies with well-warmed shoals and high mineralization levels was revealed. The species entering the Red Data Book is justified due to its location on the border of the habitat. It is proposed to promote the rarity status of the species in the region; recommendations on its conservation are given.