November, was also formally appointed chairperson of the powerful Central Military Commission.
Nearly 3000 NPC delegates from across the country gathered at the Great Hall of the People to elect and stamp Xi’s nomination, a foregone conclusion.
Votes are cast for the posts but are ceremonial, results very rarely a surprise.
Xi was elected by 2,952 votes to one, with three abstentions.
The new premier - widely expected to be Li Keqiang - is scheduled to be named on Friday, replacing Wen Jiabao.
Xi, who took over from Hu Jintao, is likely to remain President till 2022.
The largely symbolic role of Vice-President went to Li Yuanchao, considered an ally of Hu.
Xi takes over the reins of the country at a time when China and the authoritarian CPC are fraught with issues – corruption, pollution, slowing down of the economy, tense diplomatic relations with neighbours and millions of citizens in the most populous country in the world clamouring for more open and transparent governance.
During the first three months, Xi said the right things on issues like corruption and cutting down official extravagance. But whether his words will translate into action remains to be seen.
“Xi Jinping's first months in power as head of the ruling Communist Party have shown a "new style, but short on delivery so far", Jean-Pierre Cabestan of Baptist University of Hong Kong told AFP, describing him as "old wine in a new bottle".
Since becoming Party Chief, he has made high-profile tours to villages and military installations, trying to build on his people-friendly image by standing in queue for food with soldiers and visiting the homes of poor villagers.
He has made strong comments on rooting out corruption, saying it could “kill” the Party if both “flies” and “tigers” were not punished.
Huang Youyi, a member of the CPPCC (The Chinese People's Political Consultative Conference) National Committee and vice president of China International Publishing Group, said there were three main issues that Xi and the new leadership would have to focus urgently.
“The economy, corruption at all levels and the complicated international situation,” Huang told national broadcaster, China Central Television (CCTV). He added that the new leadership should explain China’s position to the leaders of other countries.
Dr Kenneth Kim of Renmin University said another important focus would be the growing income inequality in China. “It’s increasing even in the US. Decreasing taxes and increasing minimum wages might help but they are double-edged swords,” Kim told CCTV
After the formal announcement, state-run television channels and websites ran footage and stories on Xi’s life; his interactions in 2012 after 27 years with an American family Iowa, Xi kicking a football in Ireland and Xi sitting out and eating with villagers in China.