Mr Xi was introduced as the new party general secretary at Beijing's Great Hall of the People a day after the close of a week-long party congress that underlined the communists' determination to remain firmly in power.
He and the six other men who will form China's new collective leadership, all dressed in dark suits, walked in line on to the red-carpeted stage.
Mr Xi's appointment as chairman of the military commission, announced by the state Xinhua News Agency, marked a break from the recent tradition of retiring leaders holding on to the post for a transitional period to extend their influence.
It meant outgoing leader Hu Jintao would relinquish all positions of power, giving Mr Xi broader lee-way to consolidate his authority.
The once-a-decade leadership change was carefully choreographed.
It became clear Mr Xi would lead China five years ago, when he was appointed to the Standing Committee – the nation's apex of power – as the highest-ranked member who would not be of retirement age this year.