Galletti was the top scorer at the 1999 South American Youth Championship with nine goals in only eight games, ranking ahead the likes of Ronaldinho and Roque Santa Cruz as the Argentine under-20s won the competition in Paraguay.
He gained 13 caps for the full side, making his debut in 2000 and being selected to the squad that appeared in the 2005 FIFA Confederations Cup, where he played three matches for the eventual runners-up, including the final against Brazil.