Hantaviruses, members of the family Bunyaviridae, are the causative agents of hantavirus cardiopulmonary syndrome in South America. Hantaviruses are currently classified into species based on the guidelines provided by the International Committee on Taxonomy of Viruses. However, a new taxonomic system was proposed recently to classify Sigmodontinae-borne hantaviruses, which are divided currently into three phylogenetic clades corresponding to Andes, Laguna Negra, and Rio Mamore. Analyzing complete nucleocapsid gene sequences of all Sigmodontinae-borne hantaviruses, we propose the addition of a new clade and a fourth group to the already established Andes clade, allowing a better classification of the Sigmodontinae-borne hantaviruses.