Pampas deer (Ozotoceros bezoarticus) inhabit the major open habitats of South America, running from the Brazilian Cerrado to the subtropical grasslands of Uruguay and Argentina. In Brazil, the major population of this species is found in the Pantanal region, with several fragmented populations from the central to the southern regions. However, no information is available, regarding the abundance of Pampas deer in southern Brazilian Pampas or their connectivity with Pampas deer populations in other occurrence areas. Therefore, the Pampas deer population of Brazilian Pampas has not been included in the assessments made by the International Union for the Conservation of Nature thus far. In this study, we aimed to estimate the population density and abundance of the last known population of Pampas deer in Brazilian Pampas combining data from road surveys and aerial counts. Transect line estimates indicated a density of 1.50 (95% CI = 1.05-2.15 individuals/km²). The average aerial count was 1.55 individuals/km². Based on these density estimates, we further estimated that 243 Pampas deer (95% CI = [170-348]) inhabit the area effectively occupied by the spotted individuals. Our study shows that drones can be used to survey the Pampas deer population in Brazilian Pampas and presents the first population data for this species in southern Brazil. The findings of this study highlight the importance of conserving this population of O. bezoarticus along the southern border of Brazil.