Despite major advances in mammal research, there are knowledge gaps regarding distribution, composition, and the functional role of mammal species within agricultural and fragmented landscapes. Also, there is a lack of knowledge about which factors influence mammal assemblages within agricultural ecosystems. Therefore, this study aimed to estimate the contribution of forest cover, functional connectivity, drainage, and amount of sugar cane toward explaining the functional diversity of terrestrial mammals. We made an inventory of terrestrial mammals in an agricultural and fragmented landscape in an Atlantic Forest-Cerrado ecotone in southeastern Brazil, assessed the functional diversity of mammal assemblages, and proposed conservation strategies at the landscape level. Data collection occurred from September/2011 to August/2012 through a combination of complementary methods: active search; trapping stations; collection of fecal samples, which were identified by hair cuticle and fecal DNA analysis; and data from the literature. Functional diversity (FD) was calculated using a set of ecological traits including body mass, locomotion form, behavioral and dietary traits, and the environmental sensitivity of species. Akaike information criterion was used to compare generalized linear models between FD values and landscape metrics. Our results reveal a surprising insight about the role exerted by agricultural and fragmented landscapes, which still sustain impressively high biodiversity levels and a meaningful amount of ecological functions, indicating some resistance of species to pressure from the agricultural matrix and advancing urbanization. The amount of ecological functions performed by mammal species within agricultural and fragmented landscapes was similar to pristine areas and more preserved landscapes. Functional connectivity (amount of area assessed for species able to cross 200 m of matrix) was the most plausible model (wAICc = 0.873). Thus, we concluded that improving functional connectivity guarantees high FD values, and we demonstrate the importance of maintaining and restoring structural connections between fragment patches within these landscapes for species conservation and the maintenance of populations over time.