Yoshihiko Noda became the nation's 62nd prime minister Tuesday, tasked with leading the recovery from the March disaster.
In the formal balloting in the Diet, Noda won 308 votes in the Lower House but failed to win a majority in the opposition-controlled Upper House in the first round.
During a runoff against Sadakazu Tanigaki, leader of the Liberal Democratic Party, Noda just barely managed to squeeze by, winning 110 votes against Tanigaki's 107.