Incumbent Japanese Prime Minister Yoshihiko Noda was reelected as leader of the Democratic Party on Friday, retaining his post. The vote was broadcast live on Japan's NHK TV.
He is expected to launch a government reshuffle in October.
Three other candidates stood in the election, two former Agriculture Ministers - Hirotaka Akamatsu and Michihiko Kano - and former Internal Affairs and Communications Minister Kazahiro Haraguchi
Noda succeeded in being reelected despite criticism of his performance as party leader. Many have accused him of triggering a split in the party headed by influential politician Ichiro Ozawa.
Noda became the 95th post-war Japanese premier in August last year, and only the third from the Democratic Party, which won the Parliamentary elections in 2009.