A floristic survey of the Cactaceae family was carried out in the municipality of Santa Maria, Brazil, which is localized in the central region of Rio Grande do Sul state. The study was conducted between August 2017 and November 2018, during which time 14 species were recorded. Five species are on the endangered species list of Rio Grande do Sul. The threatened species are Echinopsis oxygona (Link) Zucc. Ex. Pfeiff. Otto, Parodia horstii (F. Ritter) N.P. Taylor, Parodia glaucina (F. Ritter), Hofacker M. Machado, Parodia linkii (Lehm.), R. Kiesling, and Parodia ottonis (Lehm.) N. P. Taylor. This paper presents a complete list of the species with reference to conservation status.