Arthropod-borne viruses represent the most important emerging viruses worldwide. Saint Louis encephalitis (SLEV) and West Nile (WNV) viruses are vectored by Culex spp. mosquitoes and amplified by several bird species. We carried out an extensive retrospective serosurvey study to analyze the exposure of free-ranging raptors to SLEV and WNV in central Argentina. We collected samples from eight species of raptors between 2008 and 2015. We used Plaque Reduction Neutralization Tests (PRNT) to analyze 523 plasma samples for both viruses. Of the individuals tested for WNV, 85.2% of the Swainson's Hawks (Buteo swainsoni) were positive. Fewer birds presented neutralizing antibodies against SLEV: 20.8% of the Black Vultures (Coragyps atratus), 25% of the Southern Caracaras (Caracara plancus), and 0.3% of the American Kestrels (Falco sparverius). One Swainson's Hawk was positive for both viruses. We found no neutralizing antibodies in samples from Turkey Vultures (Cathartes aura), Chimango Caracaras (Phalcoboenus chimango), Burrowing Owls (Athene cunicularia), and a Ferruginous Pygmy-Owl (Glaucidium brasilianum). Although seroprevalence varied among species, our results confirmed SLEV and WNV circulation in resident and migratory populations of raptors in central Argentina. These findings suggest the need for further studies regarding circulation and ecological characterization of these viruses in bird communities in Argentina.