Guaita was one of twelve Argentine players to represent both Argentina (four caps, one goal) and Italy (ten caps, five goals) at national level, before the practice of playing for more than one national team was banned. With Argentina, he won the 1937 South American Championship, and with the Italian national team, he scored the only goal in the semifinal match of the 1934 FIFA World Cup against Austria, before Italy went on to win the title on home soil.