Despite the fundamental nature of the home range to the biology of a species, aspects of its size, shape, and structure are not well defined in certain groups, such as subterranean rodents. These rodents, characterized by limited individual mobility and a patchy distribution of local populations, generally defend multipurpose territories in which breeding and foraging take place, increasing the chances for trade-offs among factors of habitat quality. The present study assessed the home-range size and shape of 2 species of tuco-tucos, Ctenomys australis (300–600 g) and C. talarum (100–180 g), using radiotelemetry in an area where they occur in sympatry, and explored the factors that could influence space use in these subterranean rodents. Home-range size (95% adaptive kernel) of C. australis (1,282.22 ± 1,014.83 m²) was ∼19-fold larger than that of C. talarum (66.69 ± 22.34 m²). The area covered daily by C. australis represented only about 9% of the total home-range size estimated by radiotelemetry in this study and was almost twice as large as that of C. talarum, but the area covered by the latter species represented an average of 35% of its total home-range size. Total aerial and subterranean plant biomass, plant cover, and soil hardness were significantly higher in the habitat occupied by C. talarum. Contrary to expectation, body size was not the predominant factor explaining intra- and interspecific variation in home-range size. We discuss how variation in food availability in space and time and differences in the intensity of polygyny could be more important factors shaping home-range size in this genus of subterranean rodents.