The collared peccary (Pecari tajacu) is distributed from southern USA to northern Argentina; however, in some Argentinean localities it went extinct over 50 years ago. As part of a rewilding project, two peccary herds (one captive-breed family group and one mixed group of rescued or zoo individuals) were reintroduced to the Ibera Natural Reserve, northeastern Argentina. We evaluated initial reintroduction success by assessing survival rates, site fidelity, and behavioral changes to provide recommendations for future reintroductions. After quarantine time, 10 individuals (3 males and 7 females) were brought to a pen for a soft-release in June, 2015, and each individual was fitted with a VHF collar. A second herd (2 males and 4 females) was released following the same protocol in May, 2016. We monitored post-release movements of all the individuals to obtain GPS locations every 100 min. Also scan sampling was used every 5 min to determine activity budget right after release and changes through time. The first group had monthly survival rates from 0.87 to 1 and all surviving individuals remained within the study area. For the second group, high dispersal distances yield low monthly survival rates from 0.66 to 1 with two individuals remaining within the study area. The first group showed a behavioral change from 30% to 52% foraging time and 20% to 15% traveling time, for 2015 and 2016, respectively. Our results indicate a successful reintroduction of peccaries in Argentina and future reintroductions should consider only releasing cohesive family groups to reduce mortality and dispersal.