The relation between the Antarctic Oscillation (AAO) and the precipitation in southeastern South America (SESA) is examined. The AAO influence is particularly strong during winter and late spring although of opposite sign. In particular during spring, AAO positive (negative) phases are associated with the intensification of an upper-level anticyclonic (cyclonic) anomaly, weakened (enhanced) moisture convergence and decreased (increased) precipitation over SESA. The combined influence of both ENSO and AAO on SESA precipitation was also explored and significant correlation values between both oscillations are only observed during spring. Results show that during that particular season, AAO activity produces a strong modulation of the ENSO signal on SESA precipitation.