This paper presents a taxonomic revision of the genus Tullgrenella Mello-Leito, 1941. Four new species are described: Tullgrenella aisenbergae Marta, sp. nov. (Brazil) (), T. legalissima Marta & Hagopin sp. nov. (Uruguay) (), T. galianoae Marta, sp. nov. (Brazil) () and T. sciosciae Marta & Bustamante sp. nov. (Brazil) (). The males of T. corrugata Galiano, 1981 and T. peniaflorensis Galiano, 1970, and the female of T. selenita Galiano, 1970 are described for the first time. An updated diagnosis for the genus is provided based on the detailed comparative morphological studies. In addition, we present a proposal and discussion about the species groups of Tullgrenella based on the putative synapomorphies as well as the updated distribution of the genus in South America.